Increase from 10 to 25 shards for browser_tests on Mac10.14 Tests

Bug: 1455542
Change-Id: Ib848b670e06029298c984ec1c2d675e532cdc684
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4622289
Reviewed-by: Reilly Grant <[email protected]>
Commit-Queue: Lindsay Pasricha <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1159156}
diff --git a/testing/buildbot/test_suite_exceptions.pyl b/testing/buildbot/test_suite_exceptions.pyl
index c29f3a1..86e07dd 100644
--- a/testing/buildbot/test_suite_exceptions.pyl
+++ b/testing/buildbot/test_suite_exceptions.pyl
@@ -1148,6 +1148,11 @@
           'shards': 20,  # crbug.com/1419045
         },
       },
+      'Mac10.14 Tests': {
+        'swarming': {
+          'shards': 25,  # crbug.com/1455542
+        },
+      },
       'Mac10.15 Tests': {
         # crbug.com/1042757
         'swarming': {