These were never assigned a location.  They are now removed by the
translator similar to other inactive variables.

Bug: angleproject:4313
Change-Id: I3398d06e1dea3f43b84f206cca07cde5b44b21a8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2021734Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>