nbconvert vulnerability

Security scan failing with:

```
Name      Version ID                  Fix Versions
--------- ------- ------------------- ------------
nbconvert 7.16.6  GHSA-xm59-rqc7-hhvf
```

No fix at this time, will need to add `--ignore-vuln` as a temporary security exception.  Note this only affects documentation builds on Windows, so should not affect production GH doc workflows or any user code.