Bug#846854: nagios2mantis: Don't depend on nagios3 which has been removed from unstable

[Moritz Mühlenhoff]

On Sat, Dec 03, 2016 at 06:54:26PM +0100, Bas Couwenberg wrote:
> Source: nagios2mantis
> Version: 3.1-1.1
> Severity: normal
> Tags: patch
> 
> Dear Maintainer,
> 
> Please update your package to deal with the nagios3 removal from Debian
> (#845765).

Or let's simply remove nagios2mantis, after all mantis has been removed
from Debian as well.

Cheers,
        Moritz