Delete malfunctioning Codeplex casks, fixes #6618

`pcsxr`, `wabbitemu` and `winxound` casks were using a URL that lasts only for 24 hours. These casks never worked. There is no way to get a permanent URL from [Codeplex](https://pcsxr.codeplex.com), and that means there is no way to fix these casks.