change cron job CI to run mondays only

.github/workflows/run_tests.yml

@@ -1,7 +1,7 @@
 name: Run Tests
 on:
   schedule:
-    - cron:  '0 8 * * 1-5'
+    - cron:  '0 8 * * 1'
   push:
     branches: [ main ]
   pull_request: