[TEST] Remove unnecessary submit

(cherry picked from commit 7ed7e5e31d)

src/video_core/fence_manager.h

@@ -91,9 +91,6 @@ public:
             func();
         }
         fences.push(std::move(new_fence));
-        if (should_flush) {
-            rasterizer.FlushCommands();
-        }
         if constexpr (can_async_check) {
             guard.unlock();
             cv.notify_all();