[ci] use patched artifact upload

.gitea/workflows/build-latex.yaml

@@ -16,7 +16,7 @@ jobs:
     - uses: DeterminateSystems/nix-installer-action@main
     - uses: DeterminateSystems/magic-nix-cache-action@main
     - run: "nix build .#\"${{ matrix.assignment }}\""
-    - uses: actions/upload-artifact@v4
+    - uses: christopherhx/gitea-upload-artifact@v4
       with:
         name: "${{ matrix.assignment }}"
         path: result/abgabe.pdf