Use Git history instead of Contributor: lines in each APKBUILD

At the moment we have Contributor: lines on some packages (but not all of them), but often they don't represent the actual contributors to the package very well. E.g. when we added them retroactively to the device packages we only added the initial contributor (which isn't necessarily the person who made most of the work for a device...)

IMO the Git history is the most representative source for figuring out who contributed to a package, so there is no reason to duplicate that into the APKBUILD.

I would only keep the Maintainer: listed in there (for packages that have an active maintainer).

AFAIK the same was discussed for Alpine a few times before but it just got lost at some point.