Switch pbr setup.cfg metadata to setuptools metadata

[sivel]

pbr used some differing metadata keys from what setuptools uses/documents.

Diff of the `METADATA` files included in the wheel...

--- metadata-before.txt	2023-05-16 08:55:22
+++ metadata-after.txt	2023-05-16 08:57:43
@@ -22,9 +22,46 @@
 Classifier: Topic :: System :: Systems Administration
 Classifier: Topic :: Utilities
 Requires-Python: >=3.9
+Description-Content-Type: text/markdown
 License-File: LICENSE.md
 Requires-Dist: PyYAML
 Requires-Dist: requirements-parser
 Requires-Dist: bindep
 Requires-Dist: jsonschema
 
+[![CI](https://github.com/ansible/ansible-builder/actions/workflows/ci.yml/badge.svg?branch=devel)](https://github.com/ansible/ansible-builder/actions?query=branch%3Adevel)
+[![codecov](https://codecov.io/gh/ansible/ansible-builder/branch/devel/graph/badge.svg?token=4F6P3DBI40)](https://codecov.io/gh/ansible/ansible-builder)
+
+# Ansible Builder
+
+Ansible Builder is a tool that automates the process of building execution
+environments using the schemas and tooling defined in various Ansible
+Collections and by the user.
+
+See the readthedocs page for `ansible-builder` at:
+
+https://ansible-builder.readthedocs.io/en/stable/
+
+
+## Get Involved:
+
+* We use [GitHub issues](https://github.com/ansible/ansible-builder/issues) to
+  track bug reports and feature ideas
+* Want to contribute, check out our [guide](CONTRIBUTING.md)
+* Join us in the `#ansible-builder` channel on Libera.chat IRC
+* For the full list of Ansible email Lists, IRC channels and working groups,
+  check out the [Ansible Mailing
+  lists](https://docs.ansible.com/ansible/latest/community/communication.html#mailing-list-information)
+  page of the official Ansible documentation.
+
+## Code of Conduct
+
+We ask all of our community members and contributors to adhere to the [Ansible
+code of
+conduct](http://docs.ansible.com/ansible/latest/community/code_of_conduct.html). If
+you have questions, or need assistance, please reach out to our community team
+at [codeofconduct@ansible.com](mailto:codeofconduct@ansible.com)
+
+## License
+
+[Apache License v2.0](./LICENSE.md)

Technically summary and home_page didn't need changes, but I switched them to adhere to the setup.cfg docs at https://setuptools.pypa.io/en/latest/userguide/declarative_config.html

Fixes #532

[Shrews]

Thanks! Verified on TestPyPI: https://test.pypi.org/project/ansible-builder/3.0.1/