Vulkan: Remove extraCopyBufferRegion workaround. Bug: angleproject:2838 Change-Id: I53ba3cf307f930ae9550d1bfee4650df6e826930 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3202475 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>