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] <support@github.com>

requirements.txt

@@ -41,7 +41,7 @@ mkl-service==2.3.0
 nbconvert==5.6.1
 nbformat==5.0.5
 networkx==2.4
-notebook==6.0.3
+notebook==6.4.12
 numpy==1.18.1
 olefile==0.46
 opencv-python==4.2.0.32