Refd #9 - Make the language filter list suggestions feature opt-in

Background / User story

We implemented the language filter list suggestions feature via #9 (closed). As there's concerns from ops that releasing as-is could put more pressure on our servers, we wanted to make this feature as opt-in so that users who need this can still enable this option from their Settings page.

What to change

• Spec: https://gitlab.com/eyeo/specs/spec/-/merge_requests/385
• Development:
  • adblockpluschrome/lib/prefs.js: Set the "recommend_language_subscriptions" preference value to false.
  • mocks/js/config/prefs-data.js: Set the "recommend_language_subscriptions" preference value to false.
  • See also comment for hints on what to change.

Hints for testers

We can use the same tips that have been defined here to test the functionality for users who haven't opted in and those who did opt in: https://gitlab.com/eyeo/adblockplus/abpui/adblockplusui/-/issues/9#hints-for-testers

Hints for translators

No translation changes are required.