Audit date format usage in /app/assets/javascripts/pages/users/activity_calendar.js

In /app/assets/javascripts/pages/users/activity_calendar.js we are using ~/lib/utils/datetime/date_format_utility to format dates, in most cases, our preference is to always use a util from app/assets/javascripts/lib/utils/datetime/locale_dateformat.js

In order to decide how this date should be displayed, these guidelines should be used: https://design.gitlab.com/content/date-and-time#guidelines

If it is possible to retain the same date format and use locale_dateformat, please create a merge request implementing this, if not, please comment on this issue explaining why it is not yet possible. Please note: in some cases, we can get a very similar format but not exactly the same, in this case, please create the implementation in a MR and clearly show the difference in formatting so that the reviewers can approve or suggest a change. For an implementation plan and live coding examples, please refer to the parent epic: &13978