Fix compiler warnings (#3729)

Author: russcam

docs/client-concepts/high-level/indexing/indexing-documents.asciidoc

@@ -7,7 +7,7 @@
 ////
 IMPORTANT NOTE
 ==============
-This file has been generated from https://github.com/elastic/elasticsearch-net/tree/feature/improve-docs/src/Tests/Tests/ClientConcepts/HighLevel/Indexing/Indexing.doc.cs. 
+This file has been generated from https://github.com/elastic/elasticsearch-net/tree/6.x/src/Tests/Tests/ClientConcepts/HighLevel/Indexing/IndexingDocuments.doc.cs. 
 If you wish to submit a PR for any spelling mistakes, typos or grammatical errors for this file,
 please modify the original csharp file found at the link and submit the PR with that change. Thanks!
 ////
@@ -205,12 +205,7 @@ client.BulkAll(people, b => b
       })
       .RetryDocumentPredicate((item, person) => <3>
       {
-          if (item.Error.Index == "even-index"
-              && person.FirstName == "Martijn")
-          {
-              return true;
-          }
-          return false;
+          return item.Error.Index == "even-index" && person.FirstName == "Martijn";
       })
       .DroppedDocumentCallback((item, person) => <4>
       {

docs/client-concepts/high-level/indexing/pipelines.asciidoc

@@ -17,6 +17,8 @@ please modify the original csharp file found at the link and submit the PR with
 
 An ingest pipeline is a series of processors that are to be executed in the same order as they are declared.
 
+Let's work with the following POCOs
+
 [source,csharp]
 ----
 public class Person

src/Tests/Tests/ClientConcepts/HighLevel/Indexing/IndexingDocuments.doc.cs

@@ -53,7 +53,7 @@ public async Task SingleDocument()
 		* If you need to set additional parameters when indexing you can use the fluent or object initializer syntax.
 		* This will allow you finer control over the indexing of single documents.
 		*/
-		public async Task SingleDocumentWithParameters()
+		public void SingleDocumentWithParameters()
 		{
 			var person = new Person
 			{
@@ -154,7 +154,7 @@ public async Task BulkIndexDocuments()
 		*
 		* The helper will also lazily enumerate an `IEnumerable<T>` collection, allowing you to index a large number of documents easily.
 		*/
-		public async Task BulkDocumentsWithObservableHelper()
+		public void BulkDocumentsWithObservableHelper()
 		{
                         // hide
 			var people = new []
@@ -203,7 +203,7 @@ public async Task BulkDocumentsWithObservableHelper()
 		* 2. `RetryDocumentPredicate` enables fine control on deciding if a document that failed to be indexed should be retried.
 		* 3. `DroppedDocumentCallback` in the event a document is not indexed, even after retrying, this delegate is called.
 		*/
-		public async Task AdvancedBulkIndexing()
+		public void AdvancedBulkIndexing()
 		{
 			//hide
 			var people = new[] { new Person() };
@@ -221,12 +221,7 @@ public async Task AdvancedBulkIndexing()
 				  })
 				  .RetryDocumentPredicate((item, person) => //<3> decide if a document should be retried in the event of a failure
 				  {
-					  if (item.Error.Index == "even-index"
-					      && person.FirstName == "Martijn")
-					  {
-						  return true;
-					  }
-					  return false;
+					  return item.Error.Index == "even-index" && person.FirstName == "Martijn";
 				  })
 				  .DroppedDocumentCallback((item, person) => //<4> if a document cannot be indexed this delegate is called
 				  {

src/Tests/Tests/ClientConcepts/HighLevel/Indexing/IngestNodes.doc.cs

@@ -26,7 +26,7 @@ public class IngestNodes : DocumentationTestBase
 		*
 		* The simplest way to achieve this is to create a dedicated "indexing" client instance, and use it for indexing requests.
 		*/
-		public async Task CustomClient()
+		public void CustomClient()
 		{
 			var pool = new StaticConnectionPool(new [] //<1> list of ingest nodes
 			{
@@ -45,7 +45,7 @@ public async Task CustomClient()
 		* filter out the nodes that have ingest capabilities. This allows you to customise the cluster and not have to reconfigure
 		* the client.
 		*/
-		public async Task SniffingConnectionPool()
+		public void SniffingConnectionPool()
 		{
 			var pool = new SniffingConnectionPool(new [] //<1> list of cluster nodes
 			{

src/Tests/Tests/ClientConcepts/HighLevel/Indexing/Pipelines.doc.cs

@@ -8,9 +8,11 @@
 namespace Tests.ClientConcepts.HighLevel.Caching
 {
 	/**[[pipelines]]
-	*=== Ingest Pipelines
-	*
-	* An ingest pipeline is a series of processors that are to be executed in the same order as they are declared.
+	 *=== Ingest Pipelines
+	 *
+	 * An ingest pipeline is a series of processors that are to be executed in the same order as they are declared.
+	 *
+	 * Let's work with the following POCOs
 	*/
 	public class IngestPipelines : DocumentationTestBase
 	{
@@ -46,7 +48,7 @@ public class GeoIp
 		* We could achieve this requirement by creating a custom mapping and creating an ingest pipeline.
 		* The Person type can then be used as-is, without making any changes.
 		*/
-		public async Task IngestionPipeline()
+		public void IngestionPipeline()
 		{
 			client.CreateIndex("people", c => c
 				.Mappings(ms => ms
@@ -95,7 +97,7 @@ public async Task IngestionPipeline()
 		*
 		* For large bulk requests, it could be prudent to increase the default indexing timeout to avoid exceptions.
 		*/
-		public async Task IncreasingTimeouts()
+		public void IncreasingTimeouts()
 		{
 			client.Bulk(b => b
 				.Index("people")