Source adp-docs from local checkout in playbook

Restore the local-filesystem source (`url: .`, `branches: HEAD`) for
adp-docs so the Netlify deploy preview builds the PR branch instead of
re-fetching `main`. Other sources stay on GitHub.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: micheleRP

local-antora-playbook.yml

@@ -12,8 +12,8 @@ output:
   clean: true
 content:
   sources: 
-  - url: https://github.com/redpanda-data/adp-docs
-    branches: main
+  - url: .
+    branches: HEAD
   - url: https://github.com/redpanda-data/docs
     branches: [main, v/*, shared, site-search,'!v-end-of-life/*']
   - url: https://github.com/redpanda-data/cloud-docs