Metal: Remove redundant AutoObjCObj template alias Some members were held with AutoObjCObj<T> and some with AutoObjCPtr<T *>. Use the latter. Bug: angleproject:393263506 Change-Id: I9d8d56e9ffe3281d5e9087de7959249cbb4b9bd4 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6216872 Auto-Submit: Kimmo Kinnunen <kkinnunen@apple.com> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>