vk_renderpass_cache: Bring back flushes

* Idk why they were removed

src/video_core/renderer_vulkan/vk_renderpass_cache.cpp

@@ -229,7 +229,7 @@ void RenderpassCache::EndRendering() {
     // The Mali guide recommends flushing at the end of each major renderpass
     // Testing has shown this has a significant effect on rendering performance
     if (cmd_count > 20 && instance.ShouldFlush()) {
-        // scheduler.Flush();
+        scheduler.Flush();
         cmd_count = 0;
     }
 }