Since semaphore has been supported, the code for changing
external texture layout and queue family is not necessary
anymore. So remove them.

Bug: angleproject:3289
Change-Id: I5470fa4bf7db7ee4c68f157674cf907a8e455d75
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1964655
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Michael Spang <spang@chromium.org>