Fixes example for Match.pos
Fixes example for Match.pos

Also definition; it's not a method, it's inherited from NQPMatchRole where it's defined in NQP. So not a Raku method, definitely. Closes #3506

tbrowder/doc,MasterDuke17/doc,tbrowder/doc,MasterDuke17/doc,MasterDuke17/doc,MasterDuke17/doc,tbrowder/doc,tbrowder/doc