Update 4.8+ doc that OCP supports only RHEL 7.9 worker nodes

[bobfuru]

OSDOCS-2140
(Relates to 4.7 refs to RHEL 7.9 support: #31722)

Goals:

• Communicate that OCP 4.8 GA is on RHEL 8.4 content (this should be addressed in a separate PR)
• ~~Determine where to update language that RHEL 7 workers are deprecated
  • Use modules/deprecated-feature.adoc or similar language~~ deprecation note tracked in OSDOCS-2144-Update 4.6+ sys reqs that BYO RHEL7 is deprecated #32074
  • Create separate PR for 4.8 Release Notes deprecation wording
• Minor edits for style guide consistency (<- these do not need SME or QE review)

Preview links:

• System requirements for RHEL compute nodes
  https://deploy-preview-32070--osdocs.netlify.app/openshift-enterprise/latest/machine_management/user_infra/adding-rhel-compute.html#rhel-compute-requirements_adding-rhel-compute

• Minimum resource requirements
  https://deploy-preview-32070--osdocs.netlify.app/openshift-enterprise/latest/installing/installing_bare_metal/installing-bare-metal.html#minimum-resource-requirements_installing-bare-metal

[netlify]

Deploy preview for osdocs ready!

Built with commit 25b6fe4

https://deploy-preview-32070--osdocs.netlify.app

[bobfuru]

Hi @marrusl, @katherinedube, @control-d and @miabbott PTAL at these updates for incorporating RHEL 8 support for compute machines. Thank you!

[miabbott]

Looks sane to me

[bobfuru]

The scope of this PR has decreased since inception, with the bulk of the initially proposed work either unnecessary or forthcoming in subsequent PRs. Hence, the only items changing in this PR now are A) To fix RHEL supported version (now only 7.9), and B) Minor edits for docs style.

[mburke5678]

@bobfuru A couple of nits and a question born of my ignorance. Otherwise LGTM

[bobfuru]

/cherrypick enterprise-4.8

[openshift-cherrypick-robot]

@bobfuru: new pull request created: #32145

Details

In response to this:

/cherrypick enterprise-4.8

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