Fix experiment validation test code

Fix incorrect output from experiment validation code.

Change-Id: Ia44913f94b81bd08152fe2b98da889246cb49ce9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/235340
Reviewed-by: Srujan Gaddam <srujzs@google.com>
Reviewed-by: Kevin Moore <kevmoo@google.com>
Commit-Queue: Leaf Petersen <leafp@google.com>
diff --git a/tools/experimental_features.yaml b/tools/experimental_features.yaml
index 7b6ff1b..0fd686d 100644
--- a/tools/experimental_features.yaml
+++ b/tools/experimental_features.yaml
@@ -224,7 +224,7 @@
       enum T {
         t();
         void test() {
-          print("Success");
+          print('feature enabled');
         }
       }
       void main() {
@@ -241,7 +241,7 @@
         }
       }
       void main() {
-        test(enabled : true, "Success");
+        test(enabled : true, 'feature enabled');
       }
 
   super-parameters:
@@ -256,5 +256,5 @@
         C(super.foo);
       }
       void main(){
-        print(C("Success").foo);
+        print(C('feature enabled').foo);
       }