Fix nbconvert timeout
Jobs occasionally fail w/ a timeout:
$ jupyter nbconvert --to html --execute stats.ipynb --no-input --no-prompt
[NbConvertApp] Converting notebook stats.ipynb to html
[NbConvertApp] Executing notebook with kernel: python3
[NbConvertApp] ERROR | Timeout waiting for execute reply (30s).
Runtime of NB can be long since gathering of data takes some time. Look for a way to increase timeout.