Bug#906871: xul-ext-flashblock no longer works with firefox-esr 60

[Moritz Mühlenhoff]

On Tue, Aug 21, 2018 at 09:37:01PM +0300, Adrian Bunk wrote:
> Package: xul-ext-flashblock
> Version: 1.5.20-2
> Severity: serious
> 
> XUL addons are no longer supported.

Seems dead upstream, let's remove?

Cheers,
        Moritz