api_refs.yaml: checkout the right branch before forking a new one.

Author: adriendupuis

.github/workflows/api_refs.yaml

@@ -26,6 +26,8 @@ jobs:
 
             - name: Checkout documentation
               uses: actions/checkout@v4
+              with:
+                  ref: ${{ steps.version_and_branches.outputs.base_branch }}
 
             - name: Build API Refs
               # TODO: On 5.0, update tool to handle both PHP & REST APIs