🔒 pin upload_pr_documentation.yml actions to commit SHAs

Author: paulinebm

.github/workflows/upload_pr_documentation.yml

@@ -15,7 +15,7 @@ permissions:
 
 jobs:
   build:
-    uses: huggingface/doc-builder/.github/workflows/upload_pr_documentation.yml@main
+    uses: huggingface/doc-builder/.github/workflows/upload_pr_documentation.yml@90b4ee2c10b81b5c1a6367c4e6fc9e2fb510a7e3  # main
     with:
       package_name: agents-course
       hub_base_path: https://moon-ci-docs.huggingface.co/learn