Clarifies an example (and eliminates subsectioning)

Author: JJ

doc/Language/typesystem.pod6

@@ -755,16 +755,15 @@ package, we can get a list of type objects for the keys.
     say @keys.map: *.perl;
     # OUTPUT: «(E::two E::one)␤»
 
-=head3 Introspection
-
-=head4 Metaclass
+=head3 Metaclass
 
-To test if a given type object is an enum test the meta object method C<.HOW>
-for L<Metamodel::EnumHOW|/type/Metamodel::EnumHOW>.
+To test if a given type object is an C<enum>, test the meta object method
+C<.HOW> for L<Metamodel::EnumHOW|/type/Metamodel::EnumHOW> or simply test again
+the C<Enumeration> role.
 
     enum E(<a b c>);
-    say E.HOW ~~ Metamodel::EnumHOW;
-    # OUTPUT: «True␤»
+    say E.HOW ~~ Metamodel::EnumHOW; # OUTPUT: «True␤»
+    say E ~~ Enumeration;            # OUTPUT: «True␤»
 
 =head3 Methods