change cron schedule for legacy test workflow (#5551)

The schedule for the legacy opmath test workflow was set to `0 0 2 * *`
instead of `0 2 * * *`. This makes it run on the 2nd of every month at
midnight, instead of every day at 2am. Oops. Fixed in this PR.

.github/workflows/legacy_op_math.yml

@@ -2,7 +2,7 @@ name: Legacy opmath tests
 
 on:
   schedule:
-    - cron: "0 0 2 * *"
+    - cron: "0 2 * * *"
   workflow_dispatch:
 
 jobs: