Update package_raspbian.yml to pull correct code for PR runs

.github/workflows/package_raspbian.yml

@@ -14,7 +14,12 @@ jobs:
     runs-on: ubuntu-latest
     needs: build-raspbian
     steps:
-      - uses: actions/checkout@v3
+      - name: Checkout code
+        uses: actions/checkout@v3
+        with:
+          submodules: "recursive"
+          ref: ${{github.event.pull_request.head.ref}}
+          repository: ${{github.event.pull_request.head.repo.full_name}}
 
       - name: Get release version string
         run: echo "version=$(./bin/buildinfo.py long)" >> $GITHUB_OUTPUT