Vulkan: Clean up redundant vk:: prefixes. Were in a lot of places in vk_helpers. Bug: angleproject:3944 Change-Id: I8635400d6debb7ed92e3cf84993773ca9ed74285 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1879963 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Tim Van Patten <timvp@google.com>