Inline complete method as well

For better guarantees that `finalAction` is actually called on the same
screen that `checkCanComplete()` was (uses result of one
`getCurrentScreen()` call throughout instead of calling multiple times).

osu.Game/PerformFromMenuRunner.cs

@@ -84,7 +84,8 @@ namespace osu.Game
             // we may already be at the target screen type.
             if (validScreens.Contains(current.GetType()) && !beatmap.Disabled)
             {
-                complete();
+                finalAction(current);
+                Cancel();
                 return;
             }
 
@@ -138,11 +139,5 @@ namespace osu.Game
             lastEncounteredDialogScreen = current;
             return true;
         }
-
-        private void complete()
-        {
-            finalAction(getCurrentScreen());
-            Cancel();
-        }
     }
 }