minor #3755 [Cookbook][Security] Firewall resitrction tweaks, fix markup, add to toc (xabbuh)

This PR was merged into the 2.4 branch.

Discussion
----------

[Cookbook][Security] Firewall resitrction tweaks, fix markup, add to toc

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.4+
| Fixed tickets |

Reapply some fixes to #3681 that probably got lost with #3695.

Commits
-------

612ab9b add missing toctree entry for the firewall restriction article
899bc4e fix literal

Author: weaverryan

cookbook/security/firewall_restriction.rst

@@ -65,7 +65,7 @@ matches the configured ``pattern``.
         ));
 
 The ``pattern`` is a regular expression. In this example, the firewall will only be 
-activated if the URL starts (due to the ``^`` regex character) with ``/admin`. If 
+activated if the URL starts (due to the ``^`` regex character) with ``/admin``. If
 the URL does not match this pattern, the firewall will not be activated and subsequent 
 firewalls will have the opportunity to be matched for this request.
 

cookbook/security/index.rst

@@ -12,6 +12,7 @@ Security
     acl
     acl_advanced
     force_https
+    firewall_restriction
     host_restriction
     form_login
     securing_services