[iOS][Password Сheck] Fixed crash when displaying alerts on iPads

This change fixes crashes when editing/deletion confirmation alerts are
displayed.

Bug: 1115052, 1112344
Change-Id: I3bbd31c4d37d5036655c51a3caba4de464fb9b55
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2351783Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Viktor Semeniuk <vsemeniuk@google.com>
Cr-Commit-Position: refs/heads/master@{#797189}

ios/chrome/browser/ui/settings/password/password_details/password_details_coordinator.mm

@@ -148,7 +148,8 @@
                          browser:self.browser
                            title:nil
                          message:message
-                   barButtonItem:nil];
+                   barButtonItem:self.viewController.navigationItem
+                                     .rightBarButtonItem];
 
   __weak __typeof(self) weakSelf = self;
 
@@ -177,7 +178,8 @@
                          browser:self.browser
                            title:nil
                          message:message
-                   barButtonItem:nil];
+                   barButtonItem:self.viewController.navigationItem
+                                     .rightBarButtonItem];
 
   __weak __typeof(self) weakSelf = self;