Remove partial keyword on abstract comment selection base.

src/EditorFeatures/Core/Implementation/CommentSelection/AbstractCommentSelectionBase.cs

@@ -37,7 +37,7 @@ internal enum Operation
         Undefined
     }
 
-    internal abstract partial class AbstractCommentSelectionBase
+    internal abstract class AbstractCommentSelectionBase
     {
         private readonly ITextUndoHistoryRegistry _undoHistoryRegistry;
         private readonly IEditorOperationsFactoryService _editorOperationsFactoryService;