submodule: bump third_party/openthread/repo from `0a74d66` to `dd4ce78` (#1297)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `0a74d66` to `dd4ce78`.
- [Commits](https://github.com/openthread/openthread/compare/0a74d66fedd3c9558ccf298055305a0eef5a6896...dd4ce786a8fa67c66265408a923535f4b5e980f6)

---
updated-dependencies:
- dependency-name: third_party/openthread/repo
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
diff --git a/third_party/openthread/repo b/third_party/openthread/repo
index 0a74d66..dd4ce78 160000
--- a/third_party/openthread/repo
+++ b/third_party/openthread/repo
@@ -1 +1 @@
-Subproject commit 0a74d66fedd3c9558ccf298055305a0eef5a6896
+Subproject commit dd4ce786a8fa67c66265408a923535f4b5e980f6