Fixes #1657. Don't try to test null-check pattern in irrefutable context (#1671)

Author: sgrekhov

LanguageFeatures/Patterns/list_A05_t05.dart

@@ -60,28 +60,6 @@ String test3(List list) {
 }
 
 main() {
-  var <int>[a1, b1, ... List r1?] = [1, 2, 3, 4, 5];
-  Expect.equals(1, a1);
-  Expect.equals(2, b1);
-  Expect.listEquals([3, 4, 5], r1);
-
-  final [a2, ...List<int> r2?, b2, c2] = [ 2, 3, 4, 5, 6];
-  Expect.equals(2, a2);
-  Expect.listEquals([3, 4], r2);
-  Expect.equals(5, b2);
-  Expect.equals(6, c2);
-
-  var <int>[... /* comment */ r3?, a3, b3, c3] = [1, 2, 3, 4, 5, 6];
-  Expect.listEquals([1, 2, 3], r3);
-  Expect.equals(4, a3);
-  Expect.equals(5, b3);
-  Expect.equals(6, c3);
-
-  var [... _?, a4, b4, c4] = [1, 2, 3, 4, 5, 6];
-  Expect.equals(4, a4);
-  Expect.equals(5, b4);
-  Expect.equals(6, c4);
-
   Expect.equals([5, 6].toString(), test1([1, 2, 3, 4, 5, 6]));
   Expect.equals([3, 4].toString(), test1([2, 3, 4, 5, 6]));
   Expect.equals([3, 4, 5].toString(), test1([3, 4, 5, 6, 7, 8]));