Cleanup deprecated SM-specific syntax in ExtractFormations in Commands.js

This piece of code used Array comprehensions, since deprecated, and removed in Firefox 58. See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Array_comprehensions

Patch By: smiley

Reviewed By: elexis

Differential Revision: https://code.wildfiregames.com/D1724