Follow-up from "Document additional support for Oracle Linux 8 and 9"

The following discussion from !153737 (merged) should be addressed:

• @plu8 started a discussion:

  Non-blocker:

  This could be for another MR, just noticed that we only mention OS EOL here, should we also explain or link the associated GitLab EOL? i.e. Last supported GitLab version to match the first one.