Reduce Renovate frequency to once-per-hour (#204)

The Renovate bot now runs once per hour rather than once every 15
minutes. I found that whenever I'm actively working, I prefer to
trigger runs myself, so the 15 minute frequency was getting in my way
too often. Every hour is more than often enough.

.github/workflows/renovate.yml

@@ -1,7 +1,7 @@
 name: Renovate
 on:
   schedule:
-    - cron: '0/15 * * * *'
+    - cron: '0 * * * *'
   workflow_dispatch:
 jobs:
   renovate: