[io grant] Remove mention of `role IO`
[io grant] Remove mention of `role IO`

Still need to move all the routines documented in IO.pod6
to appropriate files before nixing IO.pod6 file altogether. For now,
at least remove the mention that role IO is a thing.

stmuk/doc,tbrowder/doc,jonathanstowe/doc,MasterDuke17/doc,jonathanstowe/doc,dmaestro/doc,perl6/doc,antquinonez/doc,dmaestro/doc,tbrowder/doc,tbrowder/doc,jonathanstowe/doc,jonathanstowe/doc,tbrowder/doc,perl6/doc,MasterDuke17/doc,dmaestro/doc,MasterDuke17/doc,antquinonez/doc,gfldex/doc,gfldex/doc,antquinonez/doc,antquinonez/doc,stmuk/doc,antquinonez/doc,stmuk/doc,gfldex/doc,stmuk/doc,stmuk/doc,MasterDuke17/doc,perl6/doc,dmaestro/doc,gfldex/doc,jonathanstowe/doc,perl6/doc,perl6/doc,dmaestro/doc,gfldex/doc