Revert "First try to warn user it should close Clementine before if upgrading it"

This reverts commit 80ce992c9c844f9c2181472e602a43ba28048ce1 & ff29ea29db528f255e75624ab454cacbfe42d011.

The use of MUI_INSTALLOPTIONS_DISPLAY is no longer supported in MUI2, so this solution is not possible.