[element model] migrate `display_string_test`

Change-Id: I37dd444ee7de3463d2a40f44d6625cbb88489160
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401967
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/analyzer_use_new_elements.txt

diff --git a/pkg/analyzer/analyzer_use_new_elements.txt b/pkg/analyzer/analyzer_use_new_elements.txt
index c90c543..7624196 100644
--- a/pkg/analyzer/analyzer_use_new_elements.txt
+++ b/pkg/analyzer/analyzer_use_new_elements.txt
@@ -168,7 +168,6 @@
 test/src/dart/ast/element_locator_test.dart
 test/src/dart/constant/evaluation_test.dart
 test/src/dart/constant/value_test.dart
-test/src/dart/element/display_string_test.dart
 test/src/dart/element/element_test.dart
 test/src/dart/element/function_type_test.dart
 test/src/dart/element/generic_inferrer_test.dart