Requires GL_EXT_shadow_samplers which is not exposed by Qualcomm's
native driver on Pixel 4 XL.

Test: angle_perftests --gtest_filter="*lego_legacy*"
Bug: b/161716126
Bug: angleproject:5373
Bug: angleproject:5374
Change-Id: Ifff9c5e878b7fe9a3ade684ae5f8e57167f01a25
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2477441
Commit-Queue: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>