Amend tests testing return type of .sort

The tests were added[^1][^2] on July, 30, 2016 and are not part of 6.c.
The purpose of the tests is to check we're not returning a BOOTArray
per tickets[^3][^4], by checking the return type is a List. However,
Rakudo was changed[^5] to always return a Seq from .sort

[1] 9697a3b
[2] 94d5bc9
[3] https://rt.perl.org/Ticket/Display.html?id=126921#ticket-history
[4] https://rt.perl.org/Ticket/Display.html?id=128779#ticket-history
[5] rakudo/rakudo@434bf75b9d

S32-list/sort.t

@@ -212,11 +212,11 @@ plan 33;
 {
     my &code-method = *.sort;
     my &code-sub    =  &sort;
-    is code-method(<y z x>).^name, 'List', '.sort stored in a sub returns a List';
-    is code-sub(   <y z x>).^name, 'List', '&sort stored in a sub returns a List';
+    is code-method(<y z x>).^name, 'Seq', '.sort stored in a sub returns a List';
+    is code-sub(   <y z x>).^name, 'Seq', '&sort stored in a sub returns a List';
 }
 
 # RT #126921
-is (<2 1 3>   .sort).^name, 'List', 'detached .sort returns a List';
+is (<2 1 3>   .sort).^name, 'Seq', 'detached .sort returns a List';
 
 # vim: ft=perl6