[Crater-team] CRaTER servers to keep older operating system

[Jody Wilson]

CRaTER folks,

Mark Maciolek tried installing a newer OS (Rocky Linux) on CRaTER's 
backup servers to keep them more current, but they couldn't even boot up 
with the new system, so we're staying with CentOS 7.9.

The downside is that CentOS 7.9 becomes officially unsupported in June 
2024, so it would be more troublesome than usual to have a server fail 
after that date.

The upside is that all of the pipelines, scripts, and status pages will 
continue to function normally for now.

-Jody