fix(platform-browser): remove testing_e2e target (#10029)

The testing_e2e util does not belong in platform-browser and was never
intended to be a public API. Move it out of that whole tree.

BREAKING CHANGE:

The following API was never intended to be public and is removed:

```js
import {verifyNoBrowserErrors} from '@angular/platform-browser/testing_e2e';
```

Consider using Protractor's console plugin: https://github.com/angular/protractor-console-plugin

tools/public_api_guard/platform-browser/testing_e2e.d.ts

@@ -1,2 +0,0 @@
-/** @experimental */
-export declare function verifyNoBrowserErrors(): void;