Remove dupe of content_browsertests from Marshmallow 64 bit tester.

testing/buildbot/chromium.android.json

 {
   "Android Cronet Builder": {
     "additional_compile_targets": [
       "cronet_package"
     ]
   },
   "Android N5X Swarm Builder": {
     "gtest_tests": [
       {
         "override_compile_targets": [
@@ skipping 3565 matching lines @@
                 "=android%2Fswarming%2Flogcats%2F",
                 "${TASK_ID}%2F%2B%2Funified_logcats"
               ],
               "name": "shard #${SHARD_INDEX} logcats"
             }
           ]
         },
         "test": "content_unittests"
       },
       {
-        "override_isolate_target": "content_browsertests",
-        "swarming": {
-          "can_use_on_swarming_builders": true,
-          "cipd_packages": [
-            {
-              "cipd_package": "infra/tools/luci/logdog/butler/${platform}",
-              "location": "bin",
-              "revision": "git_revision:3ff24775a900b675866fbcacf2a8f98a18b2a16a"
-            }
-          ],
-          "dimension_sets": [
-            {
-              "device_os": "MMB29Q",
-              "device_type": "bullhead"
-            }
-          ],
-          "hard_timeout": 960,
-          "output_links": [
-            {
-              "link": [
-                "https://luci-logdog.appspot.com/v/?s",
-                "=android%2Fswarming%2Flogcats%2F",
-                "${TASK_ID}%2F%2B%2Funified_logcats"
-              ],
-              "name": "shard #${SHARD_INDEX} logcats"
-            }
-          ]
-        },
-        "test": "content_browsertests"
-      },
-      {
         "override_isolate_target": "device_unittests",
         "swarming": {
           "can_use_on_swarming_builders": true,
           "cipd_packages": [
             {
               "cipd_package": "infra/tools/luci/logdog/butler/${platform}",
               "location": "bin",
               "revision": "git_revision:3ff24775a900b675866fbcacf2a8f98a18b2a16a"
             }
           ],
@@ skipping 557 matching lines @@
       },
       {
         "test": "chrome_sync_shell_test_apk"
       },
       {
         "test": "content_shell_test_apk"
       }
     ]
   }
 }