Was mistakenly outputting UNSIGNED_BYTE. Caused incorrect rendering in
the T-Rex replay.

Bug: angleproject:3611
Change-Id: I91c91cb8b35f5f56cb4cce5b6893cef0fdbf71d8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1902187Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>