Remove `short` from reserved word list.

`short` was a future reserved word in ES 3 but not in future versions. As far as I know there's supported environment that has issues with it.

There are others that haven't been used:
"abstract", "boolean", "byte", "char", "double", "final", "float", "goto", "int", "long", "native", "short", "static", "synchronized", "throws", "transient", "volatile"