Reorder triggers in "Spell Check" workflow

No functional change, and neither is necessarily superior, but this is how it is in the "template", and so it must be
here as well.

Author: per1234

.github/workflows/spell-check-task.yml

@@ -1,8 +1,8 @@
 name: Spell Check
 
 on:
-  pull_request:
   push:
+  pull_request:
   schedule:
     # Run every Tuesday at 8 AM UTC to catch new misspelling detections resulting from dictionary updates.
     - cron: "0 8 * * TUE"