The feature names were recently updated to match their member variables,
however a few instances of "emulated_prerotation_" were missed, which
breaks using the --emulated-pre-rotation flag for dEQP tests.

Bug: b/172704839
Change-Id: I6af5cd866bff0752964e193132280f5e8fcf1528
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2536902Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>