Remove GN test from bots.

testing/buildbot/chromium_trybot.json

 {
   "compile_targets": [
     "all"
   ],
   "gtest_tests": [
     "accessibility_unittests",
     "app_list_unittests",
     {
       "test": "base_unittests",
       "swarming": {
@@ skipping 47 matching lines @@
       "platforms": ["linux"]
     },
     "device_unittests",
     "events_unittests",
     {
       "test": "extensions_unittests",
       "platforms": ["win", "mac", "linux"]
     },
     "gcm_unit_tests",
     "gfx_unittests",
-    {
-      "test": "gn_unittests",
-      "platforms": ["linux"]
-    },
     "google_apis_unittests",
     "gpu_unittests",
     {
       "test": "interactive_ui_tests",
       "exclude_builders": ["tryserver.chromium:win_chromium_x64_rel"],
       "swarming": {
         "can_use_on_swarming_builders": true,
         "shards": 3
       }
     },
@@ skipping 128 matching lines @@
     "tools/perf/.*",
     "tools/telemetry/.*",
     "tools/whitespace.txt"
   ],
 
   "filter_builders": [
     "linux_chromium_clang_dbg",
     "mac_chromium_rel"
   ]
 }