Fix 1406

Remove last vestige of Marionette.$ to fix #1406.

Confirmed that there aren't any other usages by running `grep -rn 'Marionette\.\$' .` in the project root. Also did a search through src/ and spec/ for $, just to make sure there weren't any strange usages.

I'm not sure if these tiny pull requests are actually more work for you guys, but I thought I'd open it just in case it helps.