Clarify behaviour of unlink on non-existent files
Clarify behaviour of unlink on non-existent files

Closes https://github.com/perl6/doc/issues/2096 D#2096
stmuk/doc,jonathanstowe/doc,perl6/doc,perl6/doc,dmaestro/doc,MasterDuke17/doc,stmuk/doc,tbrowder/doc,stmuk/doc,MasterDuke17/doc,dmaestro/doc,MasterDuke17/doc,dmaestro/doc,perl6/doc,MasterDuke17/doc,tbrowder/doc,jonathanstowe/doc,tbrowder/doc,tbrowder/doc,dmaestro/doc,jonathanstowe/doc,perl6/doc,jonathanstowe/doc,perl6/doc,dmaestro/doc,stmuk/doc,stmuk/doc,jonathanstowe/doc