ci: Use single comment for preview build notifications

Author: robin-nitrokey

.github/workflows/ci.yml

@@ -63,6 +63,9 @@ jobs:
         uses: thollander/actions-comment-pull-request@v3
         with:
           message: |
-            The successful documentation build was deployed for preview:
+            The successful documentation build for ${{ github.sha }} was deployed for preview:
             * https://docspreview.nitrokey.com/PR-${{ github.event.number }}
+
+            <small>workflow run ${{ github.run_id }} / attempt ${{ github.run_attempt }}</small>
+          comment-tag: preview-build