Revert "Replace $.fn.msg calls by mw.message"

This reverts commit 1804f98ee767bdf043b1b6be1cd52fa2b1b062e8.

Turned out to be a caching issue, $.fn.msg() works fine

Change-Id: I087bf5cc0bbe89fdc80c64c015218a5ff9a24ee7
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/157