Fix FieldsTest: should not search all types

The Content field is being checked for, but only the elasticsearchprojects
type contains this field.  This was causing an ArgumentNullException.

Author: gmarz

src/Tests/Nest.Tests.Integration/Search/FieldTests/FieldsTest.cs

@@ -28,7 +28,7 @@ public void Search_WithFieldsRemoved_ReturnsDocuments_ResultingArrayOfDocsShould
 					s.Skip(0)
 					.Take(10)
 					.Fields(fields.ConvertAll(x => x.ToCamelCase()).ToArray())
-					.AllTypes());
+				);
 
 			Assert.True(queryResults.IsValid);