Fix inconsistent capsule_cert example

[asteflova]

BZ#2213065 reports that an example cert file is referenced inconsistently within a single procedure. This PR attempts to fix that.

• I am familiar with the contributing guidelines.

Please cherry-pick my commits into:

• Foreman 3.7/Katello 4.9 (planned Satellite 6.14)
• Foreman 3.6/Katello 4.8
• Foreman 3.5/Katello 4.7 (Satellite 6.13)
• Foreman 3.4/Katello 4.6 (EL8 only)
• Foreman 3.3/Katello 4.5 on EL7 & EL8 (Satellite 6.12 on EL8 only; orcharhino 6.4 on EL8 only)
• Foreman 3.2/Katello 4.4 on EL7 & EL8
• Foreman 3.1/Katello 4.3 on EL7 & EL8 (Satellite 6.11 EL7/8; orcharhino 6.3 on EL7/8)
• For Foreman 3.0 or older, please create a separate PR.
• We do not accept PRs for Foreman 2.4 or older.

[github-actions]

The PR preview for c20fa04 is available at theforeman-foreman-documentation-preview-pr-2284.surge.sh

The following output files are affected by this PR:

• Installing_Proxy/index-katello.html
• Installing_Proxy/index-satellite.html

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show diff as HTML

[adamlazik1]

Merged and cherry-picked:
c416338..affc648 3.1 -> 3.1
e16bc88..7b0fd12 3.2 -> 3.2
2cc5d6d..6efbb60 3.3 -> 3.3
1e4e0e0..9683f69 3.4 -> 3.4
459e982..ac5d132 3.5 -> 3.5
99273ac..e7b16e6 3.6 -> 3.6
8353279..6cc08eb 3.7 -> 3.7