Revert "Modify user agent CTS test to (optionally) match new webview user agent."

In M and above the webview user agent should always have been updated
meaning that we should not make the check optional.

This reverts commit c45c027712010e1f0857c6a3689c617a47cf5c1d.

Bug: 20678580
Change-Id: Iad9d06af49faa572e08c39eb22e6ac99a036f122
1 file changed