Remove redundant include.
Remove redundant include.

base-call-channel.h already includes extensions.h, so .c doesn't need
to.

mlundblad/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,mlundblad/telepathy-gabble,Ziemin/telepathy-gabble