flox: update zap stanza

[tomberek]

Move full uninstallation script to "zap".

• [x] The submission is for a stable version or documented exception.
• [x] brew audit --cask --online <cask> is error-free.
• [x] brew style --fix <cask> reports no offenses.

~~Also bump to 1.0.7~~ (edit: merged elsewhere)