fix: do not list GMT as a meeting time option (ietf-tools#8507) (ietf-tools#8681)

* fix: do not list GMT as a meeting time option (ietf-tools#8507)

* chore: copyright

* chore: migration

* fix: migration conflict

---------

Co-authored-by: Jennifer Richards <jennifer@staff.ietf.org>

Author: bkmgit