updated requirements

Author: pybokeh

docker-projects/ipython_notebook/requirements.txt

@@ -22,7 +22,7 @@ matplotlib==3.1.1
 mistune==0.8.4
 nbconvert==5.5.0
 nbformat==4.4.0
-notebook==6.0.0
+notebook==6.4.1
 numpy==1.16.4
 pandas==0.24.2
 pandocfilters==1.4.2