doc: releases: fix a markdown title issue

Something got in between a chapter and its marker in a commit, fix it.

Signed-off-by: Fabio Baltieri <[email protected]>

Author: fabiobaltieri

doc/releases/release-notes-4.2.rst

@@ -59,6 +59,7 @@ Removed APIs and options
   option became the default behavior.
 
 Deprecated APIs and options
+===========================
 
 * The scheduler Kconfig options CONFIG_SCHED_DUMB and CONFIG_WAITQ_DUMB were
   renamed and deprecated. Use :kconfig:option:`CONFIG_SCHED_SIMPLE` and
@@ -67,8 +68,6 @@ Deprecated APIs and options
 * TLS credential type ``TLS_CREDENTIAL_SERVER_CERTIFICATE`` was renamed and
   deprecated, use :c:enumerator:`TLS_CREDENTIAL_PUBLIC_CERTIFICATE` instead.
 
-===========================
-
 * ``arduino_uno_r4_minima`` and ``arduino_uno_r4_wifi`` board targets have been deprecated in favor
   of a new ``arduino_uno_r4`` board with revisions (``arduino_uno_r4@minima`` and
   ``arduino_uno_r4@wifi``).