Fix build warnings

Author: russcam

src/Nest/Document/Single/Delete/DeleteResponse.cs

@@ -51,9 +51,11 @@ public class DeleteResponse : ResponseBase, IDeleteResponse
 		[JsonProperty("found")]
 		public bool Found { get; internal set; }
 
+#pragma warning disable 809 // Obsolete member overrides non-obsolete member
 		[Obsolete(@"WARNING: IsValid behavior has changed to align with 1.x and 5.x onwards.
 		It now returns true for 404 responses (document not found), where previously it returned
 		false.  Please use .Found to check whether the document was actually found.")]
 		public override bool IsValid => base.IsValid;
+#pragma warning restore 809
 	}
 }

src/Nest/Document/Single/Get/GetResponse.cs

@@ -54,9 +54,11 @@ public class GetResponse<T> : ResponseBase, IGetResponse<T> where T : class
 		public long? Timestamp { get; private set; }
 		public long? Ttl { get; private set; }
 
+#pragma warning disable 809 // Obsolete member overrides non-obsolete member
 		[Obsolete(@"WARNING: IsValid behavior has changed to align with 1.x and 5.x onwards.
 		It now returns true for 404 responses (document not found), where previously it returned
 		false.  Please use .Found to check whether the document was actually found.")]
 		public override bool IsValid => base.IsValid;
+#pragma warning restore 809
 	}
 }

src/Tests/Framework/VirtualClustering/Audit/Auditor.cs

@@ -74,7 +74,9 @@ public async Task<Auditor> TraceCall(ClientCall callTrace, int nthCall = 0)
 			return AssertAuditTrails(callTrace, nthCall);
 		}
 
+#pragma warning disable 1998 // Async method lacks 'await' operators and will run synchronously
 		private async Task TraceException<TException>(ClientCall callTrace, Action<TException> assert)
+#pragma warning restore 1998 // Async method lacks 'await' operators and will run synchronously
 			where TException : ElasticsearchClientException
 		{
 			this._cluster  = _cluster ?? this.Cluster();

src/Tests/Tests.csproj

@@ -567,7 +567,6 @@
     <Compile Include=".\Search\FieldStats\FieldStatsApiTests.cs" />
     <Compile Include=".\Search\FieldStats\FieldStatsUrlTests.cs" />
     <Compile Include=".\Search\MultiSearch\MultiSearchApiTests.cs" />
-    <Compile Include=".\Search\MultiSearch\MultiSearchInvalidApiTests.cs" />
     <Compile Include=".\Search\MultiSearch\MultiSearchLowLevelPostDataTests.cs" />
     <Compile Include=".\Search\MultiSearch\MultiSearchUrlTests.cs" />
     <Compile Include=".\Search\Percolator\MultiPercolate\MultiPercolateApiTests.cs" />
@@ -664,7 +663,6 @@
     <Compile Include="Reproduce\GithubIssue2503.cs" />
     <Compile Include="Reproduce\GithubIssue2690.cs" />
     <Compile Include="Search\Hits\HitsSerializationTests.cs" />
-    <Compile Include="Search\MultiSearch\MultiSearchApiTests.cs" />
     <Compile Include="Search\MultiSearch\MultiSearchInvalidApiTests.cs" />
     <Compile Include="Framework\Extensions\UriExtensions.cs" />
     <Compile Include="Framework\VirtualClustering\WaitingInMemoryConnection.cs" />