Metal: Remove references to GLSLANG Bug: angleproject:7220 Change-Id: Ifae4dc427e34cdd3ec17b8f897c7dec59c779633 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4104001 Reviewed-by: Gregg Tavares <gman@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Auto-Submit: Shahbaz Youssefi <syoussefi@chromium.org>