Bump notebook from 6.0.3 to 6.4.12

Bumps [notebook](http://jupyter.org) from 6.0.3 to 6.4.12.

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -33,7 +33,7 @@ markupsafe==1.1.1
 mistune==0.8.4
 nbconvert==5.6.1
 nbformat==5.0.6
-notebook==6.0.3
+notebook==6.4.12
 numpy==1.18.4
 packaging==20.3
 pandas==1.0.3