release_notes: native_sim replaces native_posix

Note that native_sim is replacing native_posix as default
test platform.

(cherry picked from commit 44aaa03)

Original-Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>
GitOrigin-RevId: 44aaa03
Change-Id: Idd6fd20eb8df552f8d5bab9e690b3c9f6961a32c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/5079634
Tested-by: Al Semjonovs <asemjonovs@google.com>
Commit-Queue: Al Semjonovs <asemjonovs@google.com>
Tested-by: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>
Reviewed-by: Al Semjonovs <asemjonovs@google.com>

doc/releases/release-notes-3.6.rst

@@ -306,5 +306,10 @@ Documentation
 Tests and Samples
 *****************
 
+* :ref:`native_sim<native_sim>` has replaced :ref:`native_posix<native_posix>` as the default
+  test platform.
+  :ref:`native_posix<native_posix>` remains supported and used in testing but will be deprecated
+  in a future release.
+
 * Fixed an issue in :zephyr:code-sample:`smp-svr` sample whereby if USB was already initialised,
   application would fail to boot properly.