Fix modules to enable OSTree content

[maximiliankolb]

What changes are you introducing?

• Drop unnecessary prerequisite about OS platform
• Drop note about Katello plugin for Hammer CLI which should be installed on Foreman/Katello Server anyway
• Fix anchor

Why are you introducing these changes? (Explanation, links to references, issues, etc.)

I stumbled over the wording as part of #3672 & the limitation to EL8/9 caught my eye which must be bogus because Foreman+Katello nightly only runs on EL9.

Anything else to add? (Considerations, potential downsides, alternative solutions you have explored, etc.)

Untested anything else than enabling the feature.

Contributor checklists

• I am okay with my commits getting squashed when you merge this PR.
• I am familiar with the contributing guidelines.

Please cherry-pick my commits into:

• Foreman 3.16/Katello 4.18 (Satellite 6.18)
• Foreman 3.15/Katello 4.17
• Foreman 3.14/Katello 4.16 (Satellite 6.17; orcharhino 7.4)
• Foreman 3.13/Katello 4.15 (EL9 only)
• Foreman 3.12/Katello 4.14 (Satellite 6.16; orcharhino 7.2 on EL9 only; orcharhino 7.3)
• Foreman 3.11/Katello 4.13 (orcharhino 6.11 on EL8 only; orcharhino 7.0 on EL8+EL9; orcharhino 7.1 with Leapp)
• Foreman 3.10/Katello 4.12
• Foreman 3.9/Katello 4.11 (Satellite 6.15; orcharhino 6.8/6.9/6.10)
• We do not accept PRs for Foreman older than 3.9.

[github-actions]

The PR preview for 7566f47 is available at theforeman-foreman-documentation-preview-pr-4309.surge.sh

The following output files are affected by this PR:

• Managing_Content/index-katello.html
• Managing_Content/index-orcharhino.html

show diff

show diff as HTML