remove predeclaration of Instant in core/IO.pm
remove predeclaration of Instant in core/IO.pm

This one hasn't been needed since
509545a46136390feef5f3c0f56943ccf6a1881a.

lucasbuchala/rakudo,sjn/rakudo,usev6/rakudo,labster/rakudo,lucasbuchala/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,ab5tract/rakudo,rakudo/rakudo,ab5tract/rakudo,azawawi/rakudo,tony-o/rakudo,lucasbuchala/rakudo,azawawi/rakudo,lucasbuchala/rakudo,tbrowder/rakudo,rakudo/rakudo,ab5tract/rakudo,tony-o/rakudo,awwaiid/rakudo,azawawi/rakudo,sjn/rakudo,samcv/rakudo,rakudo/rakudo,b2gills/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,labster/rakudo,nbrown/rakudo,b2gills/rakudo,raydiak/rakudo,jonathanstowe/rakudo,tony-o/rakudo,jonathanstowe/rakudo,nbrown/rakudo,softmoth/rakudo,Gnouc/rakudo,nbrown/rakudo,softmoth/rakudo,samcv/rakudo,MasterDuke17/rakudo,labster/rakudo,rakudo/rakudo,tbrowder/rakudo,Gnouc/rakudo,softmoth/rakudo,awwaiid/rakudo,salortiz/rakudo,raydiak/rakudo,awwaiid/rakudo,rakudo/rakudo,Gnouc/rakudo,b2gills/rakudo,awwaiid/rakudo,salortiz/rakudo,usev6/rakudo,ab5tract/rakudo,sjn/rakudo,softmoth/rakudo,tbrowder/rakudo,tbrowder/rakudo,raydiak/rakudo,samcv/rakudo,salortiz/rakudo,samcv/rakudo,usev6/rakudo,jonathanstowe/rakudo,salortiz/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,salortiz/rakudo,softmoth/rakudo,azawawi/rakudo,tbrowder/rakudo,labster/rakudo,labster/rakudo,MasterDuke17/rakudo,tony-o/rakudo,labster/rakudo,salortiz/rakudo,nbrown/rakudo,nbrown/rakudo,b2gills/rakudo,tony-o/rakudo,awwaiid/rakudo,sjn/rakudo,zostay/rakudo,MasterDuke17/rakudo,tony-o/rakudo,Gnouc/rakudo,zostay/rakudo,zostay/rakudo,azawawi/rakudo,rakudo/rakudo,zostay/rakudo,jonathanstowe/rakudo,ab5tract/rakudo,tbrowder/rakudo,usev6/rakudo,usev6/rakudo,MasterDuke17/rakudo,nbrown/rakudo,b2gills/rakudo,raydiak/rakudo,samcv/rakudo,sjn/rakudo