MFH: r448278

gecko: stop calling home to check for updates after r436423

Upstream seems to define "default" as Nightly (custom build), not safe
to update automatically. Once we switched to proper channels updater
kicked in, except Mozilla never built binaries for FreeBSD. Not to
mention, vendor updates conflict with system package manager.

PR: 221541
Approved by: ports-secteam (feld)