Merge pull request #1259 from gibiansky/dependabot/pip/notebook-6.4.1

Bump notebook from 6.1.5 to 6.4.1

requirements.txt

@@ -7,4 +7,4 @@ jupyter-client==6.1.3
 jupyter-console==6.1.0
 jupyter-core==4.6.3
 nbconvert==5.6.1
-notebook==6.1.5
+notebook==6.4.1