[SPARK-49402][PYTHON][FOLLOW-UP] Fix Binder integration in PySpark do…

…cumentation

Followup PR to add a repository for JDK

Authored-by: Hyukjin Kwon <gurwls223@apache.org>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
(cherry picked from commit 9fc1e05)
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>

binder/Dockerfile

@@ -36,6 +36,7 @@ USER ${USER}
 COPY . ${HOME}
 USER root
 RUN chown -R ${NB_UID} ${HOME}
+RUN add-apt-repository ppa:openjdk-r/ppa
 RUN apt-get update && apt-get install -y openjdk-11-jre git coreutils
 USER ${NB_USER}