Review Mozilla 1952334: Remove the old Report Site Issue fallback and its addon, and have Report Broken Site perform its function

🔍 Bugzilla Audit

Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1952334

Description

The report-site-issue extension was removed. This is an extension we also remove. We should check if there is any cleanup we need to do in our code or if the removal changes anything at all for us.

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