doc: releases: Add note for bt_le_set_auto_conn

Add note for removed function bt_le_set_auto_conn.

Signed-off-by: Emil Gydesen <[email protected]>

Author: Thalley

doc/releases/release-notes-4.3.rst

@@ -57,6 +57,7 @@ Removed APIs and options
 * The TinyCrypt library was removed as the upstream version is no longer maintained.
   PSA Crypto API is now the recommended cryptographic library for Zephyr.
 * The legacy pipe object API was removed. Use the new pipe API instead.
+* ``bt_le_set_auto_conn``
 
 Deprecated APIs and options
 ===========================