service/nvflinger: Rename GetVsyncEvent() to FindVsyncEvent()

This was missed within #2075. Renames the member function to make it
consistent with the rest of the Find* functions.

src/core/hle/service/vi/vi.cpp

@@ -1088,7 +1088,7 @@ private:
 
         LOG_WARNING(Service_VI, "(STUBBED) called. display_id=0x{:016X}", display_id);
 
-        const auto vsync_event = nv_flinger->GetVsyncEvent(display_id);
+        const auto vsync_event = nv_flinger->FindVsyncEvent(display_id);
 
         IPC::ResponseBuilder rb{ctx, 2, 1};
         rb.Push(RESULT_SUCCESS);