Reduce the number of shards for running telemetry_perf_unittest on Android bots to 1

testing/buildbot/chromium.linux.json

 {
   "Android Arm64 Builder (dbg)": {
     "additional_compile_targets": [
       "all"
     ]
   },
   "Android Builder": {
     "additional_compile_targets": [
       "cronet_test_instrumentation_apk",
       "system_webview_apk"
@@ skipping 588 matching lines @@
         "swarming": {
           "can_use_on_swarming_builders": true,
           "dimension_sets": [
             {
               "android_devices": "4",
               "device_os": "KTU84P",
               "device_type": "hammerhead"
             }
           ],
           "hard_timeout": 960,
-          "shards": 12
+          "shards": 1
         }
       }
     ],
     "junit_tests": [
       {
         "test": "base_junit_tests"
       },
       {
         "test": "chrome_junit_tests"
       },
@@ skipping 1616 matching lines @@
         "override_compile_targets": [
           "telemetry_unittests_run"
         ],
         "swarming": {
           "can_use_on_swarming_builders": true
         }
       }
     ]
   }
 }