Remove unused dynamic allocation code from GrMtlResourceProvider.

We never hit a case where uniforms are large enough to need a uniform
buffer, and we don't support any API version older than iOS 9.0 so the
backup interfaces aren't needed.

Bug: skia:10530
Change-Id: Ia5e2d61243033d30d9010b8890cd7a4fd796cb21
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307219
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
5 files changed