Update Dockerfile to include wordcloud 1.8.1

Author: surajrampure

Dockerfile

@@ -5,6 +5,7 @@ USER root
 
 RUN pip install coverage==5.5 && \
   pip install 'pandas>=0.24, <= 1.5.3' babypandas==0.1.9 pandas-tutor==2.0.3 && \
-  pip install otter-grader==3.3.0
+  pip install otter-grader==3.3.0 && \
+  pip install wordcloud==1.8.1
 
 USER $NB_UID