Mac: Blacklist all GPU features for GL <4.1

This is a very small set of machines, which have been exhibiting
- rendering artifacts when GPU compositing is enabled
- severe rendering artifacts when GPU raster is enabled

Bug: 875891
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: Ie49a9111b9723977a2b8758f824bba7843238d32
Reviewed-on: https://chromium-review.googlesource.com/1220180Reviewed-by: ccameron <ccameron@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590516}

gpu/config/software_rendering_list.json

@@ -1225,8 +1225,8 @@
     },
     {
       "id": 126,
-      "description": "Don't allow ES3 on Mac core profile < 4.1",
-      "cr_bugs": [295792],
+      "description": "Disallow use of OpenGL on Mac with core profile < 4.1",
+      "cr_bugs": [295792, 875891],
       "os": {
         "type": "macosx"
       },
@@ -1235,7 +1235,7 @@
         "value": "4.1"
       },
       "features": [
-        "accelerated_webgl2"
+        "all"
       ]
     },
     {