Fix Dependabot configuration

- Change `assignees` to `reviewers` for team support
- Simplify labels to just `dependencies` for all ecosystems

Dependabot only accepts individual usernames for assignees, but supports teams for reviewers.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: GaryJones

.github/dependabot.yml

@@ -14,8 +14,7 @@ updates:
         patterns: ["*"]
     labels:
       - "dependencies"
-      - "github-actions"
-    assignees:
+    reviewers:
       - "Automattic/vip-plugins"
     commit-message:
       prefix: "Actions"
@@ -40,7 +39,7 @@ updates:
           - "yoast/*"
     labels:
       - "dependencies"
-    assignees:
+    reviewers:
       - "Automattic/vip-plugins"
     commit-message:
       prefix: "Composer"
@@ -63,8 +62,7 @@ updates:
           - "@types/*"
     labels:
       - "dependencies"
-      - "npm"
-    assignees:
+    reviewers:
       - "Automattic/vip-plugins"
     commit-message:
       prefix: "npm"