Update actions/upload-artifact action to v7

Author: renovate[bot]

.github/workflows/ubuntu.yml

@@ -34,7 +34,7 @@ jobs:
           echo "filename=$filename" >> $GITHUB_ENV
 
       - name: Upload strfry deb
-        uses: actions/upload-artifact@v6
+        uses: actions/upload-artifact@v7
         with:
           name: ${{ env.filename }}
           path: ${{ env.filename }}