fix: correct class in bootstrap integration doc

projects/demo/src/app/integration/bootstrap/bootstrap.component.html

@@ -13,7 +13,7 @@ <h2>Integration with Bootstrap 4</h2>
 <p>
   Since we don't use HTML 5 validation but Angular validation, since Angular doesn't mark the input fields
   with <code>.is-invalid</code>, and since <code>val-errors</code> is smart enough to hide itself when the field is invalid,
-  the easiest way to deal with this is to override the <code>.is-invalid</code> class in your global stylesheet to make sure
+  the easiest way to deal with this is to override the <code>.invalid-feedback</code> class in your global stylesheet to make sure
   it's always displayed, and to configure ngx-valdemort to add the <code>invalid-feedback</code> class.
 </p>