Enable the Translate bubble UX by default

Remove the flag --enable-translate-new-ux and enable the bubble by default only for the aura environments.

BUG=276181
TEST=browser_tests --gtest_filter=TransalteManagerBrowserTest.*:TranslateBubbleViewBrowserTest.*:TranslateBrowserTest.*

Review URL: https://codereview.chromium.org/148173003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248142 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248142