Bump notebook from 6.1.5 to 6.4.12

Bumps [notebook](http://jupyter.org) from 6.1.5 to 6.4.12.

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

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

Author: dependabot[bot]

requirements.txt

@@ -130,7 +130,7 @@ murmurhash==1.0.2
 nbconvert==5.6.1
 nbformat==4.4.0
 networkx==2.2
-notebook==6.1.5
+notebook==6.4.12
 numba==0.47.0
 numexpr==2.7.0
 numpy==1.16.3