ci: reduce quicktype-core updates

quicktype-core publishes on a per commit basis. This change reduces the updates to monthly.

Author: alan-agius4

Diff for: renovate.json

@@ -21,6 +21,10 @@
     ".github/workflows/**/*.yml"
   ],
   "packageRules": [
+    {
+      "matchPackageNames": ["quicktype-core"],
+      "schedule": ["schedule:monthly"]
+    },
     {
       "groupName": "angular",
       "matchPackagePatterns": ["^@angular/.*", "angular/dev-infra"]