schedule at :30 (#5055)

Trying to get this CI task to run

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Author: Manishearth

.github/workflows/build-test.yml

@@ -27,7 +27,7 @@ on:
         - nightly
   schedule:
     # Run nightly cronjob CI every day at 14 UTC / 6AM PST / 3PM CET
-    - cron:  '24 * * * *'
+    - cron:  '30 * * * *'
     # Run beta slightly later
     - cron:  '1 * * * *'