UI: Removed unused static AddProjectorMenuMonitors declaration

e832b42 made AddProjectorMenuMonitors a member function of OBSBasic, but
the (now unused) declaration of the static function never got removed.
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f