DOC: bots: add warning to xmpp bots (#1614)
DOC: bots: add warning to xmpp bots (#1614)

Adds a warning that the xmpp bots are unmaintained

certtools/intelmq#1614

aaronkaplan/intelmq,certtools/intelmq,aaronkaplan/intelmq,certtools/intelmq,certtools/intelmq,aaronkaplan/intelmq