changelog: update

PL-133205

changelog.d/20241126_174743_PL-133205-dhcp-port-to-kea_scriv.md

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+<!--
+
+A new changelog entry.
+
+Delete placeholder items that do not apply. Empty sections will be removed
+automatically during release.
+
+Leave the XX.XX as is: this is a placeholder and will be automatically filled
+correctly during the release and helps when backporting over multiple platform
+branches.
+
+-->
+
+### Impact
+
+
+### NixOS XX.XX platform
+
+- router: the ISC DHCP server, which is end-of-life, has been replaced
+  with its successor implementation, Kea. (PL-133205)