[annotator] fix highlighting syntax

tutorials/writing_tests_for_plugins/annotator_test.md

@@ -16,7 +16,7 @@ The second is a valid prefix but an invalid key, as noted by the test `<error>`
 public class Test {
   public static void main(String[] args) {
     System.out.println("simple:website");
-        System.out.println("simple:<error descr="Unresolved property">websit"</error>);
+    System.out.println("simple:<error descr="Unresolved property">websit</error>");
   }
 }
 ```