channel.py: remove ChannelTypeContactSearch as the interface was removed from the spec
channel.py: remove ChannelTypeContactSearch as the interface was removed from the spec

freedesktop-unofficial-mirror/telepathy__telepathy-python,detrout/telepathy-python,max-posedon/telepathy-python,detrout/telepathy-python,PabloCastellano/telepathy-python,freedesktop-unofficial-mirror/telepathy__telepathy-python,max-posedon/telepathy-python,epage/telepathy-python,PabloCastellano/telepathy-python,epage/telepathy-python