Remove disable_multimonitor_multisampling driver bug workaround.

The associated code has been removed for some time and its continued
presence is confusing.

BUG=237931

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I4c2ed46f7e8882958b6e533633a60f9afe04ce36
Reviewed-on: https://chromium-review.googlesource.com/592713Reviewed-by: Victor Miura <vmiura@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490652}

gpu/config/gpu_driver_bug_list.json

 {
   "name": "gpu driver bug list",
-  "version": "10.21",
+  "version": "10.22",
   "entries": [
     {
       "id": 1,
@@ -166,17 +166,6 @@
         "swizzle_rgba_for_async_readpixels"
       ]
     },
-    {
-      "id": 30,
-      "cr_bugs": [237931],
-      "description": "Multisampling is buggy on OSX when multiple monitors are connected",
-      "os": {
-        "type": "macosx"
-      },
-      "features": [
-        "disable_multimonitor_multisampling"
-      ]
-    },
     {
       "id": 31,
       "cr_bugs": [154715, 10068, 269829, 294779, 285292],

gpu/config/gpu_driver_bug_workaround_type.h

@@ -73,8 +73,6 @@
          disable_gl_rgb_format)                              \
   GPU_OP(DISABLE_LARGER_THAN_SCREEN_OVERLAYS,                \
          disable_larger_than_screen_overlays)                \
-  GPU_OP(DISABLE_MULTIMONITOR_MULTISAMPLING,                 \
-         disable_multimonitor_multisampling)                 \
   GPU_OP(DISABLE_NON_EMPTY_POST_SUB_BUFFERS_FOR_ONSCREEN_SURFACES, \
          disable_non_empty_post_sub_buffers_for_onscreen_surfaces) \
   GPU_OP(DISABLE_NV12_DXGI_VIDEO,                            \