Shift Dependabot checks to weekly; this is a critical repo. (#205)

Author: kattni

.github/dependabot.yml

@@ -3,9 +3,10 @@ version: 2
 multi-ecosystem-groups:
   dependencies:
     schedule:
-      # Check for updates on the first Sunday of every month, 8PM UTC
-      interval: "cron"
-      cronjob: "0 20 * * sun#1"
+      # Check for updates on Sunday, 8PM UTC
+      interval: "weekly"
+      day: "sunday"
+      time: "20:00"
 
 updates:
   - package-ecosystem: "github-actions"