Update wxmac.rb

Slight version bump for wxmac from 3.0.0 to 3.0.1. Also, the patch that was previously included is now part of the wx source code and thus doesn't need to be reapplied, so I've removed the patch which shouldn't have any consequence.

Updated the SHA1.

Here's hoping the homebrew build bot doesn't hate me this time.
Let's maintain the use of the `downloads` domain.