Docs: Java pom.xml has issues

[sebastianharko]

The pom.xml in the docs (https://cloudstate.io/docs/user/lang/java/gettingstarted.html) has some issues. I was getting errors on $ mvn docker:build.

The following fixed it:

• In the "io.fabric8" plugin section, I put the "name" part below the image section and not below the build section.
• The name of the docker image is not adoptopenjdk/11-jre-hotspot with tag latest but adoptopenjdk with the tag 11-jre-hotspot.

I can make a PR to fix this.