add firewall restriction document to security toctree
fix literal
minor #3700 [Cookbook][Security] Firewall restrictions tweaks (xabbuh)

This PR was merged into the master branch.

Discussion
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[Cookbook][Security] Firewall restrictions tweaks

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.5+
| Fixed tickets |

Commits
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70b55b5 fix literal
ddf5fe4 add firewall restriction document to security toctree