Deprecate Maintainer and Contributor comments

(previous discussion: abuild#10147 (closed))

# Maintainer-comments in APKBUILD are being parsed by abuild, like any other variable in APKBUILDs. abuild already supports the maintainer-variable and for a short while maintainer variables were preferred than the Maintainer-comment. But this change was reverted as it was considered a bigger change.

# Contributor-comments are not being parsed by abuild or any other tool, it's only purpose was to credit previous contributors (and maintainers). However often contributors were forgotten to be added as a comment, and the comments only reflected contributors who remembered to add themself, or sometimes on a maintainership switch. Also as the APKBUILDs grow over time, more and more people contribute and therefore the git repository (which already is big enough) and the individual APKBUILDs grow (the largest amount of Contributors on a single aport is 8). All contributors (including previous maintainers) can be fount in the git log including the authored date and the related change. Co-authors can be added to the commit message as well. Therefore we don't need the redundant Contributor-comments.

I'd like to propose to deprecate the Maintainer-comments (as before) and the Contributor-comments. We can either remove all comments tree-wide or individually over time.