Delete unused test utilities file chrome.dart (#9372)

Author: elliette

packages/devtools_shared/lib/devtools_test_utils.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file or at https://developers.google.com/open-source/licenses/bsd.
 
-export 'src/test/chrome.dart';
 export 'src/test/chrome_driver.dart';
 export 'src/test/cli_test_driver.dart';
 export 'src/test/integration_test_runner.dart';