docs: Fix CentOS install guide
The CentOS install guide was referencing an invalid package
(`dnf-plugins-core`) so update for the yum equivalent.
Fixes
@@ -6,7 +6,7 @@ This step is only required in case Docker is not installed on the system.
1. Install the latest version of Docker with the following commands:
```bash
-$ sudo yum -y install dnf-plugins-core
+$ sudo yum -y install yum-utils
$ sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
$ sudo yum -y install docker-ce
```
