doc: release-notes-4-2: Add entry for raw IP sockets

Add bullet point about raw IP sockets support.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>

Author: rlubos

doc/releases/release-notes-4.2.rst

@@ -149,6 +149,10 @@ New APIs and options
 
     * :kconfig:option:`CONFIG_MQTT_VERSION_5_0`
 
+  * Sockets
+
+    * :kconfig:option:`CONFIG_NET_SOCKETS_INET_RAW`
+
 * Stepper
 
   * :c:func:`stepper_stop()`