Fix ErrorPageTestCase to not wait for a matcher with grey_nil()

ios/chrome/browser/ui/error_page_egtest.mm

Index: ios/chrome/browser/ui/error_page_egtest.mm
diff --git a/ios/chrome/browser/ui/error_page_egtest.mm b/ios/chrome/browser/ui/error_page_egtest.mm
index 0651839806daa22ef27d638e86bed19f9a50db9c..52fe6f1f38a2f70f69dd3062d6c6c2d34a8fdfcd 100644
--- a/ios/chrome/browser/ui/error_page_egtest.mm
+++ b/ios/chrome/browser/ui/error_page_egtest.mm
@@ -25,6 +25,7 @@
 using chrome_test_util::OmniboxText;
 using chrome_test_util::TapWebViewElementWithId;
 using chrome_test_util::WebViewContainingText;
+using chrome_test_util::WebViewNotContainingText;
 
 using web::test::HttpServer;
 
@@ -49,8 +50,8 @@ using web::test::HttpServer;
       assertWithMatcher:grey_notNil()];
   const std::string kError =
       l10n_util::GetStringUTF8(IDS_ERRORPAGES_HEADING_NOT_AVAILABLE);
-  [[EarlGrey selectElementWithMatcher:WebViewContainingText(kError)]
-      assertWithMatcher:grey_nil()];
+  [[EarlGrey selectElementWithMatcher:WebViewNotContainingText(kError)]
+      assertWithMatcher:grey_notNil()];
 }
 
 #pragma mark - tests