Apply params filters on arrays of hashes too

Modifies PR https://github.com/airbrake/airbrake/pull/306 to kick in only when the hash key being filtered is an array of hashes.
It's a special case, admitted. The current code does not filter arrays at all: https://github.com/airbrake/airbrake/blob/master/lib/airbrake/utils/params_cleaner.rb#L77