[flash] guard test #9273 against other targets

tests/unit/src/unit/issues/Issue9273.hx

@@ -8,4 +8,6 @@ class Issue9273 extends unit.Test {
 #end
 }
 
-private class HaxeExtendsSwc extends ParentCtorWithDefaultStringArgument {}
+#if flash
+private class HaxeExtendsSwc extends ParentCtorWithDefaultStringArgument {}
+#end