Allow swarming to send coverage data back to builder for Mac 10.13 Tests builder

This is mirrored by mac-rel (https://source.chromium.org/chromium/chromium/tools/build/+/master:recipes/recipe_modules/chromium_tests/trybots.py;l=1118;drc=eec8bcd5de88cb9da93b59ed44fa13b9303dfc0f)

Bug: 1024915
Change-Id: Iac6ef3b406e599418d182eca88ca5107bd8e4b10
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462985
Commit-Queue: Prakhar Asthana <pasthana@google.com>
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Auto-Submit: Prakhar Asthana <pasthana@google.com>
Reviewed-by: Yuke Liao <liaoyuke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815737}

testing/buildbot/waterfalls.pyl

@@ -4658,6 +4658,7 @@
       },
       'Mac10.13 Tests': {
         'mixins': [
+            'isolate_profile_data',
             'mac_10.13',
             'no_gpu',
         ],