Metal: Skip maximum render target size validation for Mac GPUs Only GPUs that do not support Mac families have this limitation. Bug: angleproject:8268 Change-Id: I3f9174dd104c2ba4e9781272fbc7062fe14d78a9 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4903722 Commit-Queue: Alexey Knyazev <lexa.knyazev@gmail.com> Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Kyle Piddington <kpiddington@apple.com>