chore: remove deprecated gitpod config

.gitpod.Dockerfile

-# deprecated
-FROM gitpod/workspace-full-vnc
-
-USER root
-
-RUN sudo apt-get update && sudo apt-get install -y matchbox && sudo apt-get clean && sudo rm -rf /var/cache/apt/* && sudo rm -rf /var/lib/apt/lists/* && sudo rm -rf /tmp/*
-
-USER gitpod
-
-RUN bash -c ". /home/gitpod/.sdkman/bin/sdkman-init.sh \
-             && sdk install java 16.0.1.hs-adpt \
-             && sdk default java 16.0.1.hs-adpt"

.gitpod.yml

-# deprecated
-image:
-  file: .gitpod.Dockerfile
-
-tasks:
-  - init: sdk use java 16.0.1.hs-adpt
-    command: cd javafx-template; mvn compile
-
-ports:
-  # used by virtual desktop and vnc, supports JavaFX
-  - port: 6080