update docker image to remove sync

[mishaschwartz]

Now that #143 has been merged can we please update the docker image so that the changes are reflected there?

As of right now:

$ docker run -it --rm unidata/tomcat-docker:10-jdk17 grep sync /entrypoint.sh
    sync

Thanks!

[julienchastang]

I will try to get to this, this week.