Ban deprecation warnings related to date and time formatting

app/controllers/concerns/membership_actions.rb

app/helpers/issuables_helper.rb

app/helpers/time_helper.rb

app/helpers/timeboxes_helper.rb

app/helpers/users_helper.rb

app/models/concerns/milestoneish.rb

app/models/deployment.rb

app/serializers/lfs_file_lock_entity.rb

app/services/issues/export_csv_service.rb

app/services/system_notes/time_tracking_service.rb

app/services/work_items/export_csv_service.rb

app/views/admin/groups/show.html.haml

app/views/admin/projects/show.html.haml

app/views/admin/users/_profile.html.haml

app/views/admin/users/show.html.haml

app/views/events/_event_push.atom.haml

app/views/notify/issue_due_email.html.haml

app/views/notify/repository_push_email.html.haml

app/views/notify/repository_push_email.text.haml

app/views/profiles/keys/_key_details.html.haml