Update .gitpod.Dockerfile

.gitpod.Dockerfile

 FROM gitpod/workspace-full-vnc
 
-USER gitpod
+USER root
 
 RUN add-apt-repository universe
 RUN apt update
 RUN apt install graphviz
 
+USER gitpod
+
 RUN bash -c ". /home/gitpod/.sdkman/bin/sdkman-init.sh \
              && sdk install java 14.0.2.j9-adpt \
              && sdk default java 14.0.2.j9-adpt"