Clarify how to use MultiMesh.set_instance_color.
Clarify how to use MultiMesh.set_instance_color.

Just calling set_instance_color will do nothing unless you have set
color_format and vertex_color_use_as_albedo. This is really confusing,
and I only discovered my error by finding godotengine/godot#10217 from
another confused user.

The docs should call out these requirements.

vkbsb/godot,Zylann/godot,vnen/godot,sanikoyes/godot,DmitriySalnikov/godot,sanikoyes/godot,okamstudio/godot,pkowal1982/godot,sanikoyes/godot,godotengine/godot,sanikoyes/godot,ZuBsPaCe/godot,Shockblast/godot,ex/godot,godotengine/godot,vkbsb/godot,vnen/godot,Zylann/godot,Valentactive/godot,Faless/godot,josempans/godot,godotengine/godot,vnen/godot,josempans/godot,josempans/godot,vnen/godot,MarianoGnu/godot,honix/godot,guilhermefelipecgs/godot,guilhermefelipecgs/godot,Faless/godot,okamstudio/godot,Paulloz/godot,Paulloz/godot,Valentactive/godot,ex/godot,Faless/godot,Shockblast/godot,akien-mga/godot,honix/godot,akien-mga/godot,ZuBsPaCe/godot,DmitriySalnikov/godot,akien-mga/godot,honix/godot,Shockblast/godot,BastiaanOlij/godot,MarianoGnu/godot,Paulloz/godot,ex/godot,MarianoGnu/godot,guilhermefelipecgs/godot,ex/godot,firefly2442/godot,ZuBsPaCe/godot,BastiaanOlij/godot,Zylann/godot,groud/godot,okamstudio/godot,Shockblast/godot,ex/godot,guilhermefelipecgs/godot,vnen/godot,BastiaanOlij/godot,vnen/godot,sanikoyes/godot,vkbsb/godot,ex/godot,Paulloz/godot,josempans/godot,Valentactive/godot,Paulloz/godot,Valentactive/godot,Shockblast/godot,Zylann/godot,honix/godot,DmitriySalnikov/godot,firefly2442/godot,guilhermefelipecgs/godot,Shockblast/godot,Shockblast/godot,DmitriySalnikov/godot,Zylann/godot,godotengine/godot,akien-mga/godot,guilhermefelipecgs/godot,MarianoGnu/godot,firefly2442/godot,pkowal1982/godot,godotengine/godot,Zylann/godot,josempans/godot,godotengine/godot,DmitriySalnikov/godot,groud/godot,Faless/godot,vkbsb/godot,pkowal1982/godot,okamstudio/godot,ex/godot,josempans/godot,BastiaanOlij/godot,sanikoyes/godot,godotengine/godot,BastiaanOlij/godot,Valentactive/godot,Paulloz/godot,vnen/godot,MarianoGnu/godot,vkbsb/godot,akien-mga/godot,vkbsb/godot,BastiaanOlij/godot,ZuBsPaCe/godot,MarianoGnu/godot,groud/godot,sanikoyes/godot,firefly2442/godot,okamstudio/godot,akien-mga/godot,vnen/godot,ZuBsPaCe/godot,guilhermefelipecgs/godot,ZuBsPaCe/godot,DmitriySalnikov/godot,Shockblast/godot,firefly2442/godot,BastiaanOlij/godot,pkowal1982/godot,MarianoGnu/godot,sanikoyes/godot,firefly2442/godot,ZuBsPaCe/godot,akien-mga/godot,okamstudio/godot,ZuBsPaCe/godot,ex/godot,firefly2442/godot,groud/godot,okamstudio/godot,Valentactive/godot,okamstudio/godot,Faless/godot,guilhermefelipecgs/godot,akien-mga/godot,groud/godot,godotengine/godot,pkowal1982/godot,firefly2442/godot,vkbsb/godot,Faless/godot,MarianoGnu/godot,Zylann/godot,honix/godot,DmitriySalnikov/godot,pkowal1982/godot,Faless/godot,okamstudio/godot,honix/godot,vkbsb/godot,Faless/godot,pkowal1982/godot,groud/godot,josempans/godot,Valentactive/godot,Valentactive/godot,pkowal1982/godot,josempans/godot,BastiaanOlij/godot,Zylann/godot,okamstudio/godot,Paulloz/godot