live: Remove chat support

Microsoft has been planning to drop Windows Live Messenger in favour of
Skype for quite some time now. The XMPP gateway that this provider used
does not work anymore. However, you can continue using the proprietary
MSN protocol by selecting "Others -> Windows Live (MSN)".

Fixes: https://bugzilla.gnome.org/728787
live: Don't leak the GoaDocuments

Fixes: https://bugzilla.gnome.org/728787