PowerTools repo can't be added when capitalized in CentOS8 Stream

[Kenton Tofte]

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [x] This doc is inaccurate in this way: In the example for enabling PowerTools in CentOS8, the command doesn't work when the word "PowerTools" is capitalized
- [ ] This is a doc addition request.
- [x] I have a fix to the document that I can paste below including example: input and output.

# Example command provided
yum config-manager --set-enabled PowerTools
# Alternate command that seems to work
yum config-manager --set-enabled powertools

If you have a troubleshooting or support issue, use the following resources:

 - The mailing list: https://lists.openstack.org
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-----------------------------------
Release: on 2021-02-16 18:04:49
SHA: 001d60e254923fc4e860eb1544587c18dacbf23f
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