[DOCUMENTATION] Add "Expected Findings" content for EL9

[ferricoxide]

Once plus3it/ash-linux-formula#506 is merged, watchmaker users will be able to harden EL9-based images. As with prior ELx distros, even with the supplemental-content included (via that PR), there will be several findings (see PR-comment 2148384970) that are unaddressable due to factors like:

• Finding is actually addressed but test isn't compatible with actual remediation-method
• Closing the finding would break system usability
• Finding references elements that are not relevant depending on a site's other tooling
• Finding references elements that are wholly site-local in their remediation-method
• Finding references elements for which only manual-checks possible