nixos/release-notes: remove duplicate note

Fix up the merge of the two dhcpcd hardening PRs (#336988 and #208780)

Author: rnhmjoj

nixos/doc/manual/release-notes/rl-2411.section.md

@@ -600,8 +600,6 @@
 
 - `nixosTests` now provide a working IPv6 setup for VLAN 1 by default.
 
-- `services.dhcpcd` is now started with additional systemd sandbox/hardening options for better security. When using `networking.dhcpcd.runHook` these settings are not applied.
-
 - Kanidm can now be provisioned using the new [`services.kanidm.provision`] option, but requires using a patched version available via `pkgs.kanidm.withSecretProvisioning`.
 
 - Kanidm previously had an incorrect systemd service type, causing dependent units with an `after` and `requires` directive to start before `kanidm*` finished startup. The module has now been updated in line with upstream recommendations.