adjust dependabot config

.github/dependabot.yml

@@ -1,17 +1,29 @@
 version: 2
 updates:
   # Maintain dependencies for GitHub Actions
-  - package-ecosystem: 'github-actions'
-    directory: '/'
+  - package-ecosystem: "github-actions"
+    directory: "/"
     schedule:
-      interval: 'daily'
+      interval: "weekly"
     labels:
-      - 'gh actions dependencies'
+      - "gh actions dependencies"
+    reviewers:
+      - "music-encoding/technical-team-co-chairs"
+    groups:
+      actions:
+        patterns:
+          - "*"
 
   # Maintain dependencies for Ruby
   - package-ecosystem: bundler
-    directory: /
+    directory: "/"
     schedule:
-      interval: daily
+      interval: "weekly"
     labels:
-      - 'dependencies'
+      - "dependencies"
+    reviewers:
+      - "music-encoding/technical-team-co-chairs"
+    groups:
+      bundler-dependencies:
+        patterns:
+          - "*"