Bug#906851: xul-ext-firegestures no longer works with firefox-esr 60

[Moritz Mühlenhoff]

On Tue, Aug 21, 2018 at 08:57:15PM +0300, Adrian Bunk wrote:
> Package: xul-ext-firegestures
> Version: 1.10.9-1
> Severity: serious
> 
> XUL addons are no longer supported.

Seems dead upstream, let's remove?

Cheers,
        Moritz