Add missing ansible.utils collection to requirements.yml (#14880)

The ansible.utils.ipmath filter is used in config.cfg and WireGuard
templates but the collection was not listed in requirements.yml.
This causes 'No filter named ipmath' errors for users who install
ansible-core separately rather than the full ansible package.

Fixes #14879

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

Co-authored-by: Claude <noreply@anthropic.com>

requirements.yml

@@ -2,6 +2,8 @@
 collections:
   - name: ansible.posix
     version: "==2.1.0"
+  - name: ansible.utils
+    version: ">=4.0.0"
   - name: community.general
     version: "==11.1.0"
   - name: community.crypto