Fix iPhone6 Programs test.

We shouldn't need to disable shader derivatives on iOS, so this
should fix the assert in this test.

Change-Id: Icb4fa0af3ad5822e1509f3c9857a8d52c6e85762
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/418578
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
1 file changed