Allow polygonMode* commands with active PLS Drive-by: * Test that polygonOffsetClampEXT is allowed when PLS is active. Fixed: angleproject:345253437 Change-Id: I5d9f60b3e70eaf8da19017a8b9d6c2592cb4f4f8 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5601849 Commit-Queue: Alexey Knyazev <lexa.knyazev@gmail.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>