This extension was using the key and it was used nowhere else. So moved it here and prefixed it with the extension name. Change-Id: Ia2d15b56cbf0dafd9d6e53f0e1cdd71cde331347
Procedure per https://www.mediawiki.org/wiki/Manual:GenerateJsonI18n.php with shim. Change-Id: I80e18777831bfe90c693e8ae614ccc61c3f73793