Pin actions/upload-artifact back to v3

v4+ uses the @actions/artifact v2 backend, which this self-hosted
Gitea instance rejects as unsupported since it identifies as GHES to
the action's GHES-detection check. checkout/setup-node don't have
this issue and stay on v7.

.gitea/workflows/build-release.yml

@@ -29,7 +29,7 @@ jobs:
       - name: Package appstore artifact
         run: make appstore
 
-      - uses: actions/upload-artifact@v7
+      - uses: actions/upload-artifact@v3
         with:
           name: workflow_deck_automation-${{ gitea.ref_name }}
           path: build/artifacts/appstore/*.tar.gz