Remove top-level author and contributing information

Remove AUTHORS.md and CONTRIBUTING.md as they are now covered in the
docs.

AUTHORS.md

-# repod authors
-
-* Alad Wenter <alad@archlinux.org>
-* David Runge <dvzrv@archlinux.org>
-* Felix Yan <felixonmars@archlinux.org>
-* Filipe Laíns <lains@archlinux.org>
-* Jan Alexander Steffens <heftig@archlinux.org>
-* Maxim Baz <maximbaz@archlinux.org>
-* Morten Linderud <foxboron@archlinux.org>

CONTRIBUTING.md

-# Contributing
-
-These are the contribution guidelines for repod.
-
-Development of repod takes place on Arch Linux' Gitlab:
-https://gitlab.archlinux.org/archlinux/repod.
-
-Please read our distribution-wide [Code of
-Conduct](https://terms.archlinux.org/docs/code-of-conduct/) before
-contributing, to understand what actions will and will not be tolerated.
-
-## License
-
-All code contributions fall under the terms of the **GPL-3.0-or-later** (see
-[LICENSE](LICENSE)).
-
-All documentation contributions fall under the terms of the
-**GFDL-1.3-or-later** (see [docs/LICENSE](docs/LICENSE)).
-
-All past and present authors of repod are listed in [AUTHORS.md](AUTHORS.md).
-
-## Discussion
-
-Discussion around repod takes place on the [arch-projects mailing
-list](https://lists.archlinux.org/listinfo/arch-projects) and in
-[#archlinux-projects](ircs://irc.libera.chat/archlinux-projects) on [Libera
-Chat](https://libera.chat/).
-
-## Writing code
-
-The project is written in typed Python. Please refer to [issue
-tracker](https://gitlab.archlinux.org/archlinux/repod/-/issues) for open
-tickets and ongoing development.
-
-[Tox](https://tox.readthedocs.io) and [poetry](https://python-poetry.org/) need
-to be installed to be able to test the project's code and to generate its user
-facing documentation.
-
-The code base is type checked, linted and formatted using standardized tooling.
-Please make sure to run ``tox`` before providing a merge request.
-
-For all notable changes to the code base make sure to add a
-[changelog](CHANGELOG.rst) entry in the `[Unreleased]` section. The changelog
-style follows the ["keep a changelog"](https://keepachangelog.com/en/1.0.0/)
-methodology. Valid subsection topics are:
-* **Added** for new features.
-* **Changed** for changes in existing functionality.
-* **Deprecated** for soon-to-be removed features.
-* **Removed** for now removed features.
-* **Fixed** for any bug fixes.
-* **Security** in case of vulnerabilities.
-
-### Integration for text editors
-
-An [editorconfig](https://editorconfig.org/) file is provided in this
-repository and the text editor in use should be configured to make use of it.
-
-Additional helpful integrations for linting and type checking are:
-
-* [flake8](https://flake8.pycqa.org/en/latest/)
-* [isort](https://pycqa.github.io/isort/)
-* [mypy](https://mypy.readthedocs.io/en/stable/)
-
-### Documentation
-
-All code is documented following
-[numpydoc](https://numpydoc.readthedocs.io/en/latest/) (see the accompanying
-[style guide](https://numpydoc.readthedocs.io/en/latest/format.html) for
-further info).
-
-## Writing tests
-
-Test cases are developed per module in the [tests](tests/) directory using
-[pytest](https://docs.pytest.org/) and should consist of atomic single
-expectation tests.
-Huge test cases asserting various different expectations are discouraged and
-should be split into finer grained test cases or covered using [parametrized
-tests](https://docs.pytest.org/en/latest/how-to/parametrize.html).
-
-New code additions are not accepted below 100% test coverage.
-
-The tests are distinguished between *coverage tests* and *integration tests*.
-While the former are meant to target what is commonly referred to as *unit
-tests*, the latter are meant to test more complex scenarios, involving actual
-repository actions, etc.
-
-To execute all coverage tests use
-
-```
-tox -e coverage
-```
-
-To run all integration tests use
-
-```
-tox -e integration
-```
-
-## Writing documentation
-
-Documentation is written in
-[reStructuredText](https://www.sphinx-doc.org/en/master/usage/restructuredtext/index.html)
-and assembled using
-[sphinx](https://www.sphinx-doc.org/en/master/contents.html) in the
-[docs](docs/) directory.
-
-To build the documentation use
-
-```
-tox -e docs
-```