Resolve "Handle the incorrect milestone of MRs"

What does this MR do and why?

I use a schedule task which will run every day to handle incorrect milestone of MRs.

First, according to handle-incorrect-milestone-of-mr.yml, every MR which has any milestone and is updated in past 10 days will be selected. Then I use merged_mr_has_correct_versioned_milestone? function to judge whether MR has the correct milestone. If MR doesn't have correct milestone, then jihu_set_milestone_for_merge_request will be called to add a proper milestone for this MR.

merged_mr_has_correct_versioned_milestone? will judge if the MR has an versioned milestone. Then it will call milestone_title_for_merge_request to get the proper milestone title for this MR and compare it with title of the MR which is passed to the function merged_mr_has_correct_versioned_milestone?.

Closes #33 (closed)