message: Fix OnUserQuitMessage documentation
diff: @@ -892,7 +892,7 @@ class CModule {
  */
  virtual EModRet OnUserTopicRequest(CString& sChannel);
  - /** This module hook is called when a user requests to quit from network.
  + /** This module hook is called when a client quits ZNC.
  * @since 1.7.0
  * @param Message The quit message the client sent.
  * @return See CModule::EModRet.
  