Disabling preferred languages feature (system-wide)

Description

While we introduced the preferred languages feature via translation teams efforts, some admins want to disable the preferred languages feature on their system to reduce user support costs and to silence criticism from end-users.

Proposal

We should introduce system-wide disabling the preferred languages feature.

Links / references

Documentation blurb

Overview

System-wide disabling the preferred languages feature will enables GitLab admins to save time to answer end user voice about translations.

Use cases

Some GitLab admins want this feature.

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.