RH manifest: clarify content import/export requires two different RH manifests for two orgs

[maximiliankolb]

I wanted to test exporting and importing RH content from one org to another. This failed because I could not upload the same RH manifest to the second org:

Katello::Errors::CandlepinError: org.candlepin.async.JobExecutionException: This subscription management application has already been imported by another owner.

Reproducer on Foreman/Katello 3.11/4.13:

1. Upload RH manifest to org 1 ✅
2. Upload the same RH manifest to org 2 ❌

Expected outcome: docs clarify that you cannot upload the same RH manifest on your Foreman/Katello server to multiple organizations.

⚠ Needs retesting on Foreman/Katello nightly