The .box-sizing LESS mixin was replaced by one that uses the native

box-sizing property. However, a typo was made (using @argument vs

`@arguments), causing pages to fail to load with a cryptic error

message. Now this typo has been corrected and pages load normally.
Also, since we've moved to using lessc instead of less.js,

less.js has been removed from our lib packages.

Verified pages load with this patch.