Bug#906843: xul-ext-custom-tab-width no longer works with firefox-esr 60

[Moritz Mühlenhoff]

On Tue, Aug 21, 2018 at 08:04:57PM +0300, Adrian Bunk wrote:
> Package: xul-ext-custom-tab-width
> Version: 1.1-1
> Severity: serious
> 
> XUL addons are no longer supported.

This is dead upstream and broken even in ESR, let's remove it
from the archive?

Cheers,
        Moritz