doc: release-notes: notify about Mbed TLS version upgrade

Add a note about Mbed TLS version upgrade from 3.6.4 to 3.6.5.

Signed-off-by: Valerio Setti <vsetti@baylibre.com>

Author: valeriosetti

doc/releases/release-notes-4.4.rst

@@ -100,6 +100,11 @@ New Samples
 Libraries / Subsystems
 **********************
 
+* Updated Mbed TLS from version 3.6.4 to version 3.6.5. Release notes for this
+  release can be found at the following link:
+
+  * https://github.com/Mbed-TLS/mbedtls/releases/tag/mbedtls-3.6.5
+
 Other notable changes
 *********************