Update preview-build.yml (#2347)

* Update preview-build.yml

Add           files: ${{ needs.check.outputs.added_files }} ${{ needs.check.outputs.modified_files }} to avoid checking deleted files

* Fix

* Revert files input

---------

Co-authored-by: Jan Calanog <jan.calanog@elastic.co>

Author: theletterf

.github/workflows/preview-build.yml

@@ -680,6 +680,8 @@ jobs:
         uses: actions/checkout@v6
         with:
           fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha || github.ref }}
+          persist-credentials: false
       - name: Run Vale Linter
         uses: elastic/vale-rules/lint@main
         with: