[SAC] fail2ban osgeo-trac-spam jail disabled

[Sandro Santilli]

As we found out that _DELETING_ a spam wiki page was also being
considered "offensive" by my fail2ban recipe, I disabled it
for the trac-spam checking.

Contextually, I've made sure TracSpamPlugin is enabled in each
and every instance, so from now on spam filtering should be dealth
with via the admin panel of each instance.

--strk;