Bump timeout of telemetry_perf_unittests on android_n5x bot to 20 min.

testing/buildbot/chromium.android.json

 {
   "Android Cronet Builder": {
     "additional_compile_targets": [
       "cronet_package"
     ]
   },
   "Android N5X Swarm Builder": {
     "gtest_tests": [
       {
         "override_compile_targets": [
@@ skipping 1215 matching lines @@
         ],
         "swarming": {
           "can_use_on_swarming_builders": true,
           "dimension_sets": [
             {
               "android_devices": "6",
               "device_os": "MMB29Q",
               "device_type": "bullhead"
             }
           ],
-          "hard_timeout": 960,
+          "hard_timeout": 1200,
           "shards": 1
         }
       }
     ]
   },
   "Android Swarm Builder": {
     "gtest_tests": [
       {
         "override_compile_targets": [
           "android_webview_test_apk"
@@ skipping 4102 matching lines @@
       },
       {
         "test": "chrome_sync_shell_test_apk"
       },
       {
         "test": "content_shell_test_apk"
       }
     ]
   }
 }