drop non-free

@ddevault proposed dropping the non-free section of aports. There are a few arguments that could be made to support such an action:

• Alpine should only distribute free software. Indeed, we only distribute free software in the binary package repos.
• The non-free APKBUILDs are poorly maintained. This can be observed simply by comparing the Git logs for the non-free directory by comparison to other APKBUILDs.
• Having the non-free packages as a separate project outside Alpine is likely more useful to Alpine users, as that project could decide to maintain a binary repo, etc.

The main issue at present is that it is known that users are using the non-free APKBUILDs, under the understanding that they have to build the packages themselves. If we decide to drop non-free, some sort of documentation will need to be written to address this.