Remove legacy mailbox lookup for GLImage

This was needed for Windows when DXVA video decoder produced legacy
mailboxes. DXVA video decoder has been updated so this isn't required
anymore.

Bug: 1293509
Change-Id: I7f90f644392e074905aaa015da7d1bf5dc11b534
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3856754


Commit-Queue: Kyle Charbonneau <kylechar@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1039408}