docker/jetty - removes javax.mail library provided by the docker image (

georchestra/georchestra#4233)

See georchestra/georchestra#4233 for the
context ; applying the same fix as the one on the console docker image.

web/src/docker/Dockerfile

@@ -14,6 +14,9 @@ RUN chown jetty:jetty /docker-entrypoint.d
 RUN mkdir -p /mnt/geonetwork_datadir && \
     chown jetty:jetty /mnt/geonetwork_datadir
 
+# Removes extra javax.mail library provided by Jetty
+RUN rm -rf /usr/local/jetty/lib/mail
+
 # Restore jetty user
 USER jetty