Some files were removed from the Vulkan build, so we should also
remove them. They were triggering work on incremental builds.

BUG=angleproject:1319

Change-Id: Ia179eb6d96ea2f41175c85cc8ae6313c39f68647
Reviewed-on: https://chromium-review.googlesource.com/424592Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>