[vulkan] Get tick with Flush, remove redundant call to CurrentTick.

src/video_core/renderer_vulkan/vk_fence_manager.cpp

@@ -22,8 +22,7 @@ void InnerFence::Queue() {
         return;
     }
     // Get the current tick so we can wait for it
-    wait_tick = scheduler.CurrentTick();
-    scheduler.Flush();
+    wait_tick = scheduler.Flush();
 }
 
 bool InnerFence::IsSignaled() const {