When using FRAGMENT_SHADER_DERIVATIVE_HINT_OES as a hint with
OES_standard_derivatives disabled, we should return INVALID_ENUM, not
INVALID_OPERATION.

Bug: angleproject:2158

Change-Id: I5759f1e8bb19d2caed278506054aebc5d82d431c
Reviewed-on: https://chromium-review.googlesource.com/673374Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>