An Adblock tab opens on the first launch of Icedove

An adblock tab is opened when the Debian package is installed and Icedove is started for the first time.

How should this be resolved?

1. Do we just disable the tab’s opening?; or
2. do we disable adblock completely in Icedove?

Installing enigmail—which we’ll want to do as part of the migration—will switch Icedove’s default from “HTML” to “text only”.

Feature Branch: kytv:feature/5663-return-to-icedove

Original created by @kytv on 9882 (Redmine)

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