Add Solution for lessthan30() Test in Candy Kata

[aqsa505]

Add a solution for the newly added test lessthan30 in the Candy Kata within the solution module. This test method is designed to verify the functionality of filtering and counting candies in the collection. It collects multiple bags of candy, flattens them into a single bag using flatcollect, and then filters out candies with an occurrence of less than 30.

Please note that this issue is created for GHC 2024 Open Source Day, thus priority will be given to the attendees of this event. After the event, this issue will be open to anyone.

[itsjenm]

Hello! I'd like to take this issue