channel-display: Remove deprecated init functions
channel-display: Remove deprecated init functions

They are called at the construct time since spice-common commit:
5b6be16b37370bb774aa3c2a7d5c41791fdc3a1e

fgouget/spice-gtk,fgouget/spice-gtk,flexVDI/spice-gtk,flexVDI/spice-gtk,fgouget/spice-gtk