remove erroneous my $

Author: schultzdavid

doc/Type/Attribute.rakudoc

@@ -153,7 +153,7 @@ default accessor for the attribute will return a writable value.
 
 =head2 X<trait is readonly|Traits,is readonly>
 
-    =for code :skip-test<listing>
+    =for code
     multi trait_mod:<is> (Attribute:D $attr, :readonly($)!)
 
 Marks as C<readonly> an attribute of a class that has the C<is rw> trait.
@@ -165,8 +165,8 @@ Marks as C<readonly> an attribute of a class that has the C<is rw> trait.
     };
 
     my $t = Thing.new(matter => "copper", form => "cubic");
-    my $t.form = "round";   # OK, form is rw
-    my $t.matter = "iron";  # not OK, matter is readonly
+    $t.form = "round";   # OK, form is rw
+    $t.matter = "iron";  # not OK, matter is readonly
     # OUTPUT: «Cannot modify an immutable Str (copper)␤...»
     =end code