doc: releases: Add Dummy Task Watchdog Kconfig

Add the newly introduced Dummy Task Watchdog feature Kconfig to the 4.3
release notes.

Signed-off-by: Adrien Ricciardi <[email protected]>

Author: RICCIARDI-Adrien

doc/releases/release-notes-4.3.rst

@@ -206,6 +206,10 @@ New APIs and options
 
   * :c:func:`sys_count_bits`
 
+* Task Watchdog
+
+  * :kconfig:option:`CONFIG_TASK_WDT_DUMMY`
+
 .. zephyr-keep-sorted-stop
 
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