Vulkan: Enable StateChangeTest.DisablingBufferedVertexAttribute. This was likely fixed with default vertex attribute support. Bug: angleproject:2650 Change-Id: Ibbc19013ed8227c6fe32ae186b0fa88e5c837589 Reviewed-on: https://chromium-review.googlesource.com/1200369 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>