fix recommended dependency install commands

[aep-sunlife]

libyaml-devel is an important requirement for the default Ruby installation.

Please consider moving that package into the dnf/yum install commands noted for RHEL 8 and RHEL 9.

The current README is confusing, treating that requirement as a FAQ rather than an ordinary instruction step.

[mislav]

Hi, anyone is welcome to edit the wiki, and you are welcome to add libyaml-devel to the install commands for RHEL 8 and RHEL 9 if that's what is needed for these systems. I'm surprised no one pointed that out until now.

After you edit the wiki, you may close this issue. Thank you!

The current README is confusing, treating that requirement as a FAQ rather than an ordinary instruction step.

Yeah, it's not ideal that ruby-build users can't just immediately install Ruby and have the system dependencies get actually resolved for them, but as you see from the current state of the wiki, every OS seems to want something different, and also the names of those packages can change between OS versions, and we don't want to track all of that from ruby-build's own source code. For now, we prefer that setting up a build environment is left to our users.