Renamed supportsIOSGPUFamily to supportsAppleGPUFamily
to match official naming.

Bug: angleproject:5672
Change-Id: Ic02c0f01bc30c12cef594cc2eb4f9932c22c1e33
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2739459Reviewed-by: Le Hoang Quyen <le.hoang.q@gmail.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>