Don't advertize GL_APPLE_clip_distance on direct metal The direct metal backend does not support gl_ClipDistance array. Bug: angleproject:5505 Change-Id: I9a1736bd70ee3543ecbe82b36b6ea30df0dac3c8 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3152216 Commit-Queue: Gregg Tavares <gman@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org>