[ios blink] Re-enable IOSurface GMBs

Now that IOSurfaces are mapped in the GPU process and only the
associated shared memory region is used in the renderer process, they
can be re-enabled for Blink on iOS.

Bug: 40254930
Cq-Include-Trybots: luci.chromium.try:ios-blink-rel-fyi
Change-Id: I6a6a69642f23159134b73b816078881018223763
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6631143
Auto-Submit: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1491653}