[iOS] Mark workaround as non-iOS 13 only

The UIKit bug has been fixed in iOS 13, the workaround is no longer
needed.

Bug: 931173
Change-Id: Ie14df79e34a2b107a2e4733ced44509484062ce3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1649534
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#667112}

ios/chrome/browser/ui/settings/settings_root_table_view_controller.mm

@@ -155,9 +155,12 @@ NSString* const kSettingsToolbarDeleteButtonId =
 
 - (void)viewDidLayoutSubviews {
   [super viewDidLayoutSubviews];
-  // TODO(crbug.com/931173): This is a workaround to fix the vertical alignment
-  // of the back button. Remove once the UIKit bug is fixed.
-  [self.navigationController.navigationBar setNeedsLayout];
+  if (@available(iOS 13, *)) {
+  } else {
+    // This is a workaround to fix the vertical alignment of the back button.
+    // The bug has been fixed in iOS 13. See crbug.com/931173 if needed.
+    [self.navigationController.navigationBar setNeedsLayout];
+  }
 }
 
 #pragma mark - UITableViewDelegate