Update shaderoperator_common_functions suppression.

It should be applied on all macOS versions, not just Sierra. This
affects the following WebGL 2.0 conformance test:
  deqp/functional/gles3/shaderoperator/common_functions.html

Tbr: kainino@chromium.org
Bug: 820225
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Ib0ff46c871d8ab74e56026aff96cd150e61a33d9
Reviewed-on: https://chromium-review.googlesource.com/1152452Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578864}

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -643,7 +643,7 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
     # self.Fail('conformance2/rendering/texture-switch-performance.html',
     #     ['mac', 'amd'], bug=735483)
     self.Fail('deqp/functional/gles3/shaderoperator/common_functions.html',
-        ['sierra', 'amd'], bug=820225)
+        ['mac', 'amd'], bug=820225)
     self.Fail('deqp/functional/gles3/transformfeedback/' +
         'array_interleaved_lines.html',
         ['sierra', 'amd'], bug=483282)