Repair Shippable

[stevenschwenke]

Change https://github.com/stevenschwenke/JavaFXWorkshop/blob/master/shippable.yml according to https://github.com/Shippable/support/issues/1447 to avoid

build_ci 0s apt-get update 0s
E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied) E: Unable to lock directory /var/lib/apt/lists/ E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?