Display footer copyright notice in user language on mobile

Previously, both the desktop and mobile copyright notices were
displayed in the content language rather than the user language.
In May, this was switched on desktop per Bug 49116. This change
keeps the mobile interface in sync with desktop by also displaying
the copyright notice in the user language.

Bug: 49116
Change-Id: I683137b1dbe1d55941db1777a3eea09aeaa2b5ee
Merge "Display footer copyright notice in user language on mobile"