1802: remove intervalInMinues
1802: remove intervalInMinues

with `plugins.click_to_play` deprecated in FF69, no-one here is sure if `intervalInMinutes` still applies to Flash or even works, and no-one here cares about Flash. Happy to let Mozilla just keep restricting it more and more until it's deprecated in early 2020. Note: we already disable flash anyway in pref 1803.
ghacksuserjs/ghacks-user.js,ghacksuserjs/ghacks-user.js