Less frequent Renovate (#1729)

Author: trask

.github/renovate.json5

@@ -8,10 +8,13 @@
   "ignorePresets": [":ignoreModulesAndTests"], // needed to keep maven-extension test pom files up-to-date
   "packageRules": [
     {
-      // this is to reduce the number of renovate PRs by consolidating them into a weekly batch
-      "matchManagers": ["github-actions"],
+      // this is to reduce the number of renovate PRs
+      "matchManagers": [
+        "github-actions",
+        "dockerfile"
+      ],
       "extends": ["schedule:weekly"],
-      "groupName": "github actions"
+      "groupName": "weekly update"
     },
     {
       "matchPackageNames": [