ci: run legacy saucelabs for every build (#29270)

Recently we moved the Saucelabs job into a cronjob in order to avoid
heavy flakiness that we experienced due to a Saucelabs connect bug
that has been supposedly fixed by the Saucelabs team (no new version
is released yet though).

Our initial assumption was that we very rarely hit specific browser failures
and can therefore move the Saucelabs tests into a cronjob, but after some
days of having the cronjob, we realized that we actually hit browser-specific
failures quite often and that we should run the tests for every PR (like before)

PR Close #29270

.circleci/config.yml

@@ -541,6 +541,9 @@ workflows:
       - test_aio:
           requires:
           - setup
+      - legacy-unit-tests-saucelabs:
+          requires:
+          - setup
       - deploy_aio:
           requires:
             - test_aio
@@ -593,24 +596,9 @@ workflows:
             # Get the artifacts to publish from the build-packages-dist job
             # since the publishing script expects the legacy outputs layout.
             - build-npm-packages
+            - legacy-unit-tests-saucelabs
             - legacy-misc-tests
 
-  saucelabs_tests:
-    jobs:
-      - setup
-      - legacy-unit-tests-saucelabs:
-          requires:
-            - setup
-    triggers:
-      - schedule:
-          # Runs the Saucelabs legacy tests every hour. We still want to run Saucelabs
-          # frequently as the caretaker needs up-to-date results when merging PRs or creating
-          # a new release. Also we primarily moved the Saucelabs job into a cronjob that doesn't
-          # run for PRs, in order to ensure that PRs are not affected by Saucelabs flakiness or
-          # incidents. This is still guaranteed (even if we run the job every hour).
-          cron: "0 * * * *"
-          filters: *publish_branches_filter
-
   aio_monitoring:
     jobs:
       - aio_monitoring