Drop unused method Workspace::waitForCompositingSetup

Seems to have been used in old compositing kcm, documented as DBus API.
But Workspace doesn't expose a DBus interface anymore and our new DBus
interface does not call this method -> it is dead.

workspace.cpp

@@ -803,24 +803,6 @@ void Workspace::reconfigure()
     reconfigureTimer.start(200);
 }
 
-/**
- * This D-Bus call is used by the compositing kcm. Since the reconfigure()
- * D-Bus call delays the actual reconfiguring, it is not possible to immediately
- * call compositingActive(). Therefore the kcm will instead call this to ensure
- * the reconfiguring has already happened.
- */
-bool Workspace::waitForCompositingSetup()
-{
-    if (reconfigureTimer.isActive()) {
-        reconfigureTimer.stop();
-        slotReconfigure();
-    }
-    if (m_compositor) {
-        return m_compositor->isActive();
-    }
-    return false;
-}
-
 /**
  * Reread settings
  */

workspace.h

@@ -301,7 +301,6 @@ public:
     SessionInfo* takeSessionInfo(Client*);
 
     // D-Bus interface
-    bool waitForCompositingSetup();
     QString supportInformation() const;
 
     void setCurrentScreen(int new_screen);