Update dandi download URL for testing data

Author: stephprince

.github/workflows/run_inspector_tests.yml

@@ -36,7 +36,7 @@ jobs:
           python -m pip install pytest
           python -m pip install ".[dandi]"  # this might install a pinned version of pynwb instead of the current one
           # Download testing data and set config path
-          dandi download "https://gui-staging.dandiarchive.org/#/dandiset/204919"
+          dandi download "https://sandbox.dandiarchive.org/dandiset/204919"
           cd ..
           python -m pip uninstall -y pynwb  # uninstall the pinned version of pynwb
           python -m pip install .  # reinstall current branch of pynwb