Always update the WebView's SSL certificate, regardless of whether a WebViewClient has been set

This looks like a copy-paste error from other CallbackProxy methods which call
back to the WebViewClient or WebChromeClient, rather than the WebView.

Also remove '@hide' annotations. These are superfluous as the class is not
public.

Bug: 5287216
Change-Id: If97c4d769cf82563b9c182ba09fc742fbb7e08e9