go/types: fix a comment of Named.Obj

// TypeName returns ...
-> // Obj returns ...

Change-Id: I2ac6133a703ec2c4b2045d4bdf9acc70049f0e1e
Reviewed-on: https://go-review.googlesource.com/18704
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

go/types/type.go

@@ -398,7 +398,7 @@ func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
 	return typ
 }
 
-// TypeName returns the type name for the named type t.
+// Obj returns the type name for the named type t.
 func (t *Named) Obj() *TypeName { return t.obj }
 
 // NumMethods returns the number of explicit methods whose receiver is named type t.