Remove v5 from docs
Remove v5 from docs

It's bittrotten and pointing to it just causes confusion.
https://irclog.perlgeek.de/perl6/2017-02-06#i_14052737
gfldex/doc,stmuk/doc,dmaestro/doc,jonathanstowe/doc,dmaestro/doc,perl6/doc,jonathanstowe/doc,tbrowder/doc,stmuk/doc,gfldex/doc,antquinonez/doc,stmuk/doc,perl6/doc,jonathanstowe/doc,stmuk/doc,antquinonez/doc,antquinonez/doc,perl6/doc,tbrowder/doc,gfldex/doc,perl6/doc,dmaestro/doc,antquinonez/doc,jonathanstowe/doc,gfldex/doc,MasterDuke17/doc,MasterDuke17/doc,dmaestro/doc,gfldex/doc,perl6/doc,stmuk/doc,tbrowder/doc,antquinonez/doc,MasterDuke17/doc,tbrowder/doc,dmaestro/doc,jonathanstowe/doc,MasterDuke17/doc