Do not call SafeYield on close

wxSafeYield() is not "safe".  Pending actions may include deletion of
the currently active class.  This will cause crashes when exiting.  If
needed for specific behaviors, we should use wxSafeYieldFor( flag ) with
the appropriate events specified rather than a general yield which can
cause more problems

(cherry picked from commit 9864337914)

kicad/kicad_manager_frame.cpp

@@ -410,9 +410,6 @@ bool KICAD_MANAGER_FRAME::CloseProject( bool aSave )
     if( !Kiway().PlayersClose( false ) )
         return false;
 
-    // Give a timeslice for the save-changes? dialog (and for the project to actually close)
-    wxSafeYield();
-
     // Save the project file for the currently loaded project.
     if( m_active_project )
     {