[ios] Use +[ShellEarlGrey loadURL:] for page loading in EG tests.

ios/web/shell/test/plugin_placeholder_egtest.mm

Index: ios/web/shell/test/plugin_placeholder_egtest.mm
diff --git a/ios/web/shell/test/plugin_placeholder_egtest.mm b/ios/web/shell/test/plugin_placeholder_egtest.mm
index e1eee1f5a917828206971f2a57bb476fae62d93d..b7939ec0b993d24f3cce7249bf1fb5508ba9b23f 100644
--- a/ios/web/shell/test/plugin_placeholder_egtest.mm
+++ b/ios/web/shell/test/plugin_placeholder_egtest.mm
@@ -11,8 +11,8 @@
 #include "base/test/ios/wait_util.h"
 #import "ios/web/public/test/http_server.h"
 #include "ios/web/public/test/http_server_util.h"
-#include "ios/web/shell/test/app/navigation_test_util.h"
 #import "ios/web/shell/test/earl_grey/shell_base_test_case.h"
+#import "ios/web/shell/test/earl_grey/shell_earl_grey.h"
 #import "ios/web/shell/test/earl_grey/shell_matchers.h"
 #include "url/gurl.h"
 
@@ -30,7 +30,7 @@ void LoadPage(const std::string& page_content) {
   const GURL url = web::test::HttpServer::MakeUrl("http://plugin");
   std::map<GURL, std::string> responses{{url, page_content}};
   web::test::SetUpSimpleHttpServer(responses);
-  web::shell_test_util::LoadUrl(url);
+  [ShellEarlGrey loadURL:url];
 }
 
 }  // namespace