In MDL-72810, the three-month calendar pseudo block was removed from the calendar page and the following were deprecated as a result:

• fake_block_threemonths() method from calendar/renderer.php.
• calendar/amd/src/calendar_threemonth.js - whole file.
• calendar_threemonth and threemonth_month calendar Mustache templates.
• Behat step definitions _i_hover_over_day_of_this_month_in_calendar_ and _i_click_day_of_this_month_in_calendar_.

This issue is to remove those items now they have reached final deprecation.