spice.proto: Don't use @fixedsize for Brush
spice.proto: Don't use @fixedsize for Brush

There is no reason to send the maximum size on the network, that is just
a waste of space most of the time.

fgouget/spice-protocol,fgouget/spice-protocol,vdiot/spice-protocol,SPICE/spice-protocol,SPICE/spice-protocol,SPICE/spice-protocol,vdiot/spice-protocol,vdiot/spice-protocol,fgouget/spice-protocol