Vulkan: Remove SyncHelper::mEvent Now that inserting a sync object incurs a flush, we can use the serial to perform synchronization. Bug: angleproject:6464 Bug: angleproject:6481 Change-Id: I8c82a12855b6497861ce34854d165af82956b384 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3212573 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com>