Ask users to choose a pronoun instead of sex in the Account settings panel

Summary: Fixes T4845, Use "choose a pronoun" prompt for (grammatical) gender selection instead of "Sex"

Test Plan: Open Account settings panel, expand Pronoun dropdown, verify that options are "<username> updated their/her/his profile". Switch to different language, verify that pronouns propogate

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T4845

Differential Revision: https://secure.phabricator.com/D8920