HADOOP-17246. Addendum patch for branch-3.3.

dev-support/docker/Dockerfile

@@ -168,7 +168,6 @@ RUN apt-get -q update \
 ####
 RUN pip2 install \
     astroid==1.6.6 \
-    isort==4.3.21 \
     configparser==4.0.2 \
     pylint==1.9.2 \
     isort==4.3.21