Interp static local var breaks backwards compatibility with haxe 4.2

Flixel CI (haxe 4.2, html5) is getting an error at [Interp.hx:63](https://github.com/HaxeFoundation/hscript/blob/master/hscript/Interp.hx#L63):
>  /home/runner/haxe/haxelib/hscript/git/hscript/Interp.hx:63: characters 4-10 : Expected }

If hscript wants to officially stop supporting 4.2, HaxeFlixel will likely follow suit, but this is a pretty easy fix. I can create a PR sometime today