fix typo in Groovy Dockerfile
fix typo in Groovy Dockerfile

byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web,byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web,byran/cyber-dojo-web,cyber-dojo/web,byran/cyber-dojo-web,byran/cyber-dojo-web,byran/cyber-dojo-web