remove unnecessary argument in behaviors

`lt.objs.plugins/load-js` is unary. The second argument (`true`) is ignored.

https://github.com/LightTable/LightTable/blob/6ffe995111ebf831fcd269359dc1d7019762fee3/src/lt/objs/plugins.cljs#L542
Merge pull request #5 from DomKM/patch-1

You are correct.  Thank you!