ci: set pre-commit autoupdate schedule to monthly

I find every week is a bit too much busy work for my liking. The next smallest time period is monthly.

Author: ahal

.pre-commit-config.yaml

@@ -4,6 +4,7 @@
 ci:
   autofix_commit_msg: "style: pre-commit.ci auto fixes [...]"
   autoupdate_commit_msg: "chore: pre-commit autoupdate"
+  autoupdate_schedule: monthly
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v4.5.0