How to allow browsers to cache Craft's admin static files?
I don't think it's a great idea to disable this cache busting; they put it in there for a reason.  However, if you really need/want to do it, instead of modifying Craft, I'd just configure Apache/Nginx to discard the query string for paths that match /admin/resources/

https://wiki.apache.org/httpd/RewriteQueryString