Disable Add-ons menu item in the Unsafe Browser

At the moment the add-ons manager is broken (#9307 (closed)), and in general we do not want add-ons installed in the Unsafe Browser any way, so let’s hide the menu item.

Feature Branch: feature/9305-hide-addons-manager-in-unsafe-browser

Related issues

Related to #9031 (closed)
Related to #9306 (closed)

Original created by @anonym on 9305 (Redmine)

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