manifest: net: openthread: Regular openthread upmerge to 3873c6f.

Regular openthread upmerge to `3873c6fcd5a8a9dd01b71e8efe32ef5dc7923bb1`.

(cherry picked from commit 54d9fe3)

Original-Signed-off-by: Przemyslaw Bida <przemyslaw.bida@nordicsemi.no>
GitOrigin-RevId: 54d9fe3
Change-Id: Id9556396c8b1ff8218c952e4cfbb0c6d233ff15c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/5621385
Reviewed-by: Jeremy Bettis <jbettis@chromium.org>
Commit-Queue: Jeremy Bettis <jbettis@chromium.org>
Tested-by: Jeremy Bettis <jbettis@chromium.org>
Tested-by: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>

west.yml

@@ -306,7 +306,7 @@ manifest:
       revision: da78aea63159771956fe0c9263f2e6985b66e9d5
       path: modules/lib/open-amp
     - name: openthread
-      revision: 49c59ec519cc8b49dd58978d1bc80b7ae7ba88d0
+      revision: 3873c6fcd5a8a9dd01b71e8efe32ef5dc7923bb1
       path: modules/lib/openthread
     - name: percepio
       path: modules/debug/percepio