Remove List.batch method, as it is obsolete.

src/core/List.pm

@@ -140,12 +140,6 @@ augment class List does Positional {
     multi method hash() {
         my %h = self;
     }
-
-    # CHEAT: Get the lazy list tests that depend on .batch
-    # up and running in the new system.
-    our method batch($n) {
-        self[(^$n).list];
-    }
 }