Fix warnings_checker.dart handling of multitests

tests/language/literal_unary_plus_test.dart

Index: tests/language/literal_unary_plus_test.dart
diff --git a/tests/language/literal_unary_plus_test.dart b/tests/language/literal_unary_plus_test.dart
index de484e6b42dad51ccc702761c79022e1699aec52..6c1932e5c1c9aa2241f1b7206b409f4cd3c035ee 100644
--- a/tests/language/literal_unary_plus_test.dart
+++ b/tests/language/literal_unary_plus_test.dart
@@ -6,8 +6,8 @@
 // Only a number literal can be preceded by a "+'".
 
 main() {
-  var a = + 1; //      /// 01: compile-time error
-  var x = +"foo"; //   /// 02: compile-time error
-  var x = + "foo"; //  /// 03: compile-time error
+  var a = + 1; //      //# 01: compile-time error
+  var x = +"foo"; //   //# 02: compile-time error
+  var x = + "foo"; //  //# 03: compile-time error
 }