[devtools] Check if podman needs to be used as root

The 3 compilers docs contain chapters about installing container images. Previously the images were based on Docker, and users needed to pull them as root.

We've switched to podman now, but the instructions remained the same. Our errata suggest that users run the following command as root:

podman pull registry.access.redhat.com/devtools/rust-toolset-rhel7

Is it necessary? To be confirmed by the SMEs and edit the docs if needed.
Possible contact: QA engineer for DevTools compilers Edjunior Machado (emachado).