concurrency improvement

In case of simultaneous triggered workflows keep only the latest
for a corresponding openssl branch and cancel prior ones.

Author: quarckster

.github/workflows/deploy-site.yaml

@@ -11,11 +11,15 @@ on:
 permissions:
   contents: write
 
+concurrency:
+  group: deploy-${{ github.event.inputs.branch }}
+  cancel-in-progress: false
+
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: "Fetch gh-pages branch"
         run: git fetch origin gh-pages --depth=1
       - name: "Set permissions"