message: Clarify that RenameOptions is not backwards-compatible
  RenameOptions should only used by the server if the client has
  `prepareSupport` enabled for textDocument/rename requests.
diff: @@ -821,7 +821,9 @@ export interface _ServerCapabilities {
  moreTriggerCharacter?: string[]
  };
  /**
  - * The server provides rename support.
  + * The server provides rename support. RenameOptions may only be
  + * specified if the client states that it supports
  + * `prepareSupport` in its initial `initialize` request.
  */
  renameProvider?: boolean | RenameOptions;
  /**
  