doc: release-notes-4.2: Information about TC shim

Add information about the removal of the TinyCrypt crypto driver.

Signed-off-by: Flavio Ceolin <flavio.ceolin@gmail.com>

Author: ceolin

doc/releases/release-notes-4.2.rst

@@ -107,6 +107,10 @@ Deprecated APIs and options
   pending TX buffers is now aligned with the :kconfig:option:`CONFIG_BT_BUF_ACL_TX_COUNT` Kconfig
   option.
 
+* The :kconfig:option:`CONFIG_CRYPTO_TINYCRYPT_SHIM` Kconfig option has been removed. It
+  was deprecated since Zephyr 4.0, and users were advised to migrate to alternative
+  crypto backends.
+
 New APIs and options
 ====================