Update needed for “OpenStack packages for RHEL and CentOS in Installation Guide”

[Jiaming Zhang]

Since 2023.1 release (antelope) supports RHEL / CentOS 9, information needs to be updated. With the currently provided code, 2023.1-antelope would not be installed. As per my validation, the following code would install the latest version of OpenStack on RHEL / CentOS 9:
`# dnf install https://www.rdoproject.org/repos/rdo-release.el9s.rpm`

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- [ ] This doc is inaccurate in this way: ______
- [x] This is a doc addition request.
- [ ] I have a fix to the document that I can paste below including example: input and output.

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-----------------------------------
Release: on 2023-04-19 11:47:37
SHA: f11811c4a7b17f711629364139c407652cf690dd
Source: https://opendev.org/openstack/openstack-manuals/src/doc/install-guide/source/environment-packages-rdo.rst
URL: https://docs.openstack.org/install-guide/environment-packages-rdo.html