Broken yum config-manager command on CentOS 7

[singhsegv]

- What I did
"yum config-manager" to "yum-config-manager"

- How I did it

- How to verify it

- Description for the changelog

The install script seems to be broken on CentOS 7. It results in "--add-repo not found" error. The actual issue seems from be about config-manager command not being there even after installation of yum-utils

No such command: config-manager. Please use /usr/bin/yum --help

Installing yum-utils should enable yum config-manager command in later versions of the OS (haven't tested) but it doesn't do it on the CentOS 7. This PR is to point this issue out and maybe someone can test on the newers OS versions if yum-config-manager is good to go or not. Thanks.

- A picture of a cute animal (not mandatory but encouraged)

[thaJeztah]

Doh! Looks like I broke this in b982474, which was part of;

• add support for dnf5 (in preparation of fedora 41) #441

I should warn though that we no longer support CentOS 7 (which was the last distro using yum) as it reached EOL, so no updated packages will be published, and the portions of the script that use yum may eventually be removed.

So if you're still running CentOS 7 (or 8), make sure you update to a supported distro.

[thaJeztah]

LGTM, thanks!