remove net/p5-Net-XMPP and net/p5-Net-Jabber

[Solene Rapenne]

I removed net/sendxmpp which had net/p5-Net-XMPP as a run dependency,
however p5-Net-XMPP is used by p5-Net-Jabber but the latter doesn't
have any reverse dep.

I suggest to remove both as we have no programs using them in ports.

ok?