Bump notebook from 6.1.5 to 6.4.1 in /docs_rtd (#3302)
Bump notebook from 6.1.5 to 6.4.1 in /docs_rtd (#3302)

Bumps [notebook](http://jupyter.org) from 6.1.5 to 6.4.1.

---
updated-dependencies:
- dependency-name: notebook
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
Co-authored-by: Ben Horkley <bfd4640d7f1f19e61ae24387fe3345893761ee86@superconductive.com>
great-expectations/great_expectations,great-expectations/great_expectations,great-expectations/great_expectations,great-expectations/great_expectations