ci: hardcode SERVER_URL as a workflow env var instead of an Actions variable

.gitea/workflows/release.yml

@@ -4,6 +4,9 @@ on:
   push:
     branches: [main]
 
+env:
+  SERVER_URL: https://git.arthurerlich.de
+
 jobs:
   release:
     runs-on: ubuntu-latest
@@ -76,7 +79,7 @@ jobs:
         if: steps.version.outputs.skip == 'false'
         uses: akkuman/gitea-release-action@v1
         with:
-          server_url: ${{ vars.SERVER_URL }}
+          server_url: ${{ env.SERVER_URL }}
           token: ${{ secrets.RELEASE_TOKEN }}
           tag_name: ${{ steps.version.outputs.tag }}
           name: ${{ steps.version.outputs.tag }}