[keyserver] enable Brotli compression for all users

Summary:
Follow-up to D9294.

Some context in ENG-5018.

Removing isStaff check, but leaving hasMinCodeVersion.

Clients should be able to handle this, see code here.

Test Plan: Used app for a while and make sure everything works.

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13111