Vulkan: Remove BarrierType This was only used for one ASSERT, which is changed to use a correlated variable. Bug: angleproject:4959 Change-Id: I0eccd2c06c52fcfbff4c533e661735bf1213125d Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2371222 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>