ci: use actions/upload-artifact@v4 for the Windows/CUDA artifact

The internal Gitea action is referenced as actions/upload-artifact@v4 (no
gitea- prefix), per its own documentation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitea/workflows/build_and_test.yml

@@ -101,7 +101,7 @@ jobs:
         # Keep the Windows/CUDA installer downloadable from every run (not just tagged releases) so it
         # can be grabbed and tested. Short retention - it is a throwaway test build, not a release.
         if: matrix.variant == 'cuda'
-        uses: actions/gitea-upload-artifact@v4
+        uses: actions/upload-artifact@v4
         with:
           name: jfjoch-viewer-windows-cuda-installer
           path: build/jfjoch-viewer-*-win64-cuda*.exe