Move from LitUp.DocumentationVersion to Program.DocVersion like on master and 6.x

Author: Mpdreamz

src/CodeGeneration/DocGenerator/AsciiDoc/GeneratedAsciidocVisitor.cs

@@ -76,7 +76,7 @@ public override void Visit(Document document)
 
 			if (document.Attributes.All(a => a.Name != "ref_current"))
 			{
-				_newDocument.Attributes.Add(new AttributeEntry("ref_current", $"https://www.elastic.co/guide/en/elasticsearch/reference/{LitUp.DocumentationVersion}"));
+				_newDocument.Attributes.Add(new AttributeEntry("ref_current", $"https://www.elastic.co/guide/en/elasticsearch/reference/{Program.DocVersion}"));
 			}
 
 			if (document.Attributes.All(a => a.Name != "xpack_current"))

src/CodeGeneration/DocGenerator/LitUp.cs

@@ -15,8 +15,6 @@ namespace DocGenerator
 {
 	public static class LitUp
 	{
-		public const string DocumentationVersion = "5.6";
-
 		private static readonly string[] SkipFolders = { "Debug", "Release" };
 
         private static string GetProjectDir(string projectName) => Path.Combine(Program.InputDirPath, projectName);

src/CodeGeneration/DocGenerator/Program.cs

@@ -61,7 +61,7 @@ static Program()
 
 		public static string BranchName { get; }
 
-		public static string DocVersion => "6.1";
+		public static string DocVersion => "5.6";
 
 		static int Main(string[] args)
 		{