ios: Better matcher for iOS14 bookmarks test.

Change-Id: I7b2aa098037f0bfd89b46b360493c6ec3fc24834
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354515
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797784}

ios/chrome/browser/ui/bookmarks/bookmark_earl_grey_ui.mm

@@ -388,8 +388,8 @@ id<GREYMatcher> SearchIconButton() {
       selectElementWithMatcher:grey_allOf(
                                    grey_kindOfClassName(@"UITableViewCell"),
                                    grey_descendant(grey_text(bookmarkFolder)),
-                                   nil)]
-      assertWithMatcher:grey_sufficientlyVisible()];
+                                   grey_sufficientlyVisible(), nil)]
+      assertWithMatcher:grey_notNil()];
 }
 
 - (void)scrollToBottom {