Set the number of shards for telemetry_unittest on Windows & Mac to be 2

testing/buildbot/chromium.win.json

Index: testing/buildbot/chromium.win.json
diff --git a/testing/buildbot/chromium.win.json b/testing/buildbot/chromium.win.json
index ae763043318d0beba556d0faa12067559baf1490..957053fe24569f4cacfdd592b5568e57d1b8b216 100644
--- a/testing/buildbot/chromium.win.json
+++ b/testing/buildbot/chromium.win.json
@@ -472,7 +472,8 @@
           "telemetry_unittests_run"
         ],
         "swarming": {
-          "can_use_on_swarming_builders": true
+          "can_use_on_swarming_builders": true,
+          "shards": 2
         }
       }
     ],
@@ -1390,7 +1391,8 @@
           "telemetry_unittests_run"
         ],
         "swarming": {
-          "can_use_on_swarming_builders": true
+          "can_use_on_swarming_builders": true,
+          "shards": 2
         }
       }
     ],
@@ -1780,7 +1782,8 @@
           "telemetry_unittests_run"
         ],
         "swarming": {
-          "can_use_on_swarming_builders": true
+          "can_use_on_swarming_builders": true,
+          "shards": 2
         }
       }
     ]