Remove registering upstream

[jafiala]

What changes are you introducing?

Remove registration from upstream proxy installation

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

Separate PR that was part of install-containerized-proxy

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

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 3.19/Katello 4.21
• Foreman 3.18/Katello 4.20 (Satellite 6.19; orcharhino 7.9)
• Foreman 3.17/Katello 4.19
• Foreman 3.16/Katello 4.18 (Satellite 6.18; orcharhino 7.6, 7.7, and 7.8)
• Foreman 3.15/Katello 4.17
• Foreman 3.14/Katello 4.16 (Satellite 6.17; orcharhino 7.4; orcharhino 7.5)
• We do not accept PRs for Foreman older than 3.14.

[github-actions]

The PR preview for 595f8e5 is available at theforeman-foreman-documentation-preview-pr-5115.surge.sh

The following output files are affected by this PR:

• Installing_Proxy/index-katello.html

show diff

show diff as HTML

[ekohl]

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

FYI: I asked for this. Today in upstream a content proxy doesn't pull content from the Katello server but instead directly from the internet. That makes me think the registration isn't needed and we can simplify the process. However, I may be missing something.

To keep the containerized PR simple, I've asked @jafiala to open a separate PR so we can look at it independently.

[maximiliankolb]

style-wise LGTM. I am not sure if the macros can be simplified, but IMO it's OK as is.

[ekohl]

Isn't this redundant now?

Suggested change

	endif::[]
	ifdef::satellite[]
	For more information, see xref:registering-{smart-proxy-context}-server[].
	endif::[]

Though arguably, the whole prerequisite to have it registered is now only true for Satellite, isn't it?