message: [lldb][NFC] Update documentation of Handle[Argument]Completion
  We no longer have return values or any of the mentioned arguments
  in these functions since the introduction of CompletionRequest.
diff: @@ -228,25 +228,15 @@ public:
  ///
  /// \param[in/out] request
  /// The completion request that needs to be answered.
  - ///
  - /// FIXME: This is the wrong return value, since we also need to make a
  - /// distinction between
  - /// total number of matches, and the window the user wants returned.
  virtual void HandleCompletion(CompletionRequest &request);
  - /// The input array contains a parsed version of the line. The insertion
  - /// point is given by cursor_index (the index in input of the word containing
  - /// the cursor) and cursor_char_position (the position of the cursor in that
  - /// word.)
  + /// The input array contains a parsed version of the line.
  + ///
  /// We've constructed the map of options and their arguments as well if that
  /// is helpful for the completion.
  ///
  /// \param[in/out] request
  /// The completion request that needs to be answered.
  - ///
  - /// FIXME: This is the wrong return value, since we also need to make a
  - /// distinction between
  - /// total number of matches, and the window the user wants returned.
  virtual void
  HandleArgumentCompletion(CompletionRequest &request,
  OptionElementVector &opt_element_vector) {}
  