Fix regression on trigger form error display on form validation (#37672)

(cherry picked from commit 8f5d7d2)

airflow/www/views.py

@@ -2230,6 +2230,7 @@ def trigger(self, dag_id: str, session: Session = NEW_SESSION):
                 form_fields=form_fields,
                 **render_params,
                 conf=request_conf,
+                form=form,
             )
 
         flash(f"Triggered {dag_id}, it should start any moment now.")