Fix warnings_checker.dart handling of multitests

tests/language/final_is_not_const_test.dart

Index: tests/language/final_is_not_const_test.dart
diff --git a/tests/language/final_is_not_const_test.dart b/tests/language/final_is_not_const_test.dart
index bc92d365a82d62dd3550cf0d79f027bf7321bc3d..433d4d06c2723d5b2d9bb8400d6bf977f35e61c9 100644
--- a/tests/language/final_is_not_const_test.dart
+++ b/tests/language/final_is_not_const_test.dart
@@ -5,9 +5,9 @@
 import "package:expect/expect.dart";
 
 final F0 = 42;
-const C0 = F0; // /// 01: compile-time error
+const C0 = F0; // //# 01: compile-time error
 
 main() {
   Expect.equals(42, F0);
-  Expect.equals(42, C0); // /// 01: continued
+  Expect.equals(42, C0); // //# 01: continued
 }