Update README.md with latest conformance version on Vulkan backend Bug: b/254527832 Change-Id: Ia46cef9326a323773202e067a75f715f1336e485 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4972656 Commit-Queue: Yuxin Hu <yuxinhu@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>