Remove METAO_ASSIGN caching
Remove METAO_ASSIGN caching

As discussed on #perl6-dev just now, it may cache a block that has a
incorrect version of the op, even though the name is the same.

salortiz/rakudo,rakudo/rakudo,nbrown/rakudo,MasterDuke17/rakudo,nbrown/rakudo,tbrowder/rakudo,rakudo/rakudo,nbrown/rakudo,tbrowder/rakudo,tbrowder/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,nbrown/rakudo,Gnouc/rakudo,rakudo/rakudo,nbrown/rakudo,labster/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,labster/rakudo,salortiz/rakudo,Gnouc/rakudo,labster/rakudo,softmoth/rakudo,tony-o/rakudo,salortiz/rakudo,salortiz/rakudo,MasterDuke17/rakudo,labster/rakudo,tony-o/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,softmoth/rakudo,rakudo/rakudo,tony-o/rakudo,tony-o/rakudo,tbrowder/rakudo,labster/rakudo,rakudo/rakudo,tbrowder/rakudo,tony-o/rakudo,Gnouc/rakudo,softmoth/rakudo,nbrown/rakudo,rakudo/rakudo,salortiz/rakudo,softmoth/rakudo,salortiz/rakudo,softmoth/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,tony-o/rakudo,labster/rakudo