Add release note on Metal resource tracking change

Bug: skia:12253
Change-Id: Iaf7cb2f2f3ee9310cc5edc8425d7123d11857055
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/438537
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
1 file changed