[nrf fromtree] doc: update migration guide with mesh dependency

Commit adds description of the mesh dependency on
the secure storage subsytem.

Signed-off-by: Aleksandr Khromykh <[email protected]>
(cherry picked from commit f983045)

Author: alxelax

doc/releases/migration-guide-4.1.rst

@@ -305,6 +305,11 @@ Bluetooth Mesh
   set as deprecated. Default option for platforms that do not support TF-M
   is :kconfig:option:`CONFIG_BT_MESH_USES_MBEDTLS_PSA`.
 
+* Mesh explicitly depends on the Secure Storage subsystem if storing into
+  non-volatile memory (:kconfig:option:`CONFIG_BT_SETTINGS`) is enabled and
+  Mbed TLS library (:kconfig:option:`CONFIG_BT_MESH_USES_MBEDTLS_PSA`) is used.
+  Applications should be built with :kconfig:option:`CONFIG_SECURE_STORAGE` enabled.
+
 Bluetooth Audio
 ===============