Refs #960 - Exclude Opera from language filter list suggestions

Background / User story

We've implemented Language filter list suggestions but discovered an issue for our Opera users (https://gitlab.com/eyeo/adblockplus/abpui/adblockplusui/-/issues/960), where we're unable to detect implicit web page language in Opera. This means that for our Opera users, the language filter list suggestions feature won't work.

We have reported the issue to Opera but until we have a response (and a fix), we will need to exclude the feature for these users.

What to change

• Design: N/A
• Research: N/A
• Spec: https://gitlab.com/eyeo/specs/spec/-/merge_requests/373
• Legal: N/A

Hints for testers

None.

Hints for translators

N/A