submodule: bump third_party/openthread/repo from `6f909a1` to `2caf6b8` (#1852)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `6f909a1` to `2caf6b8`.
- [Commits](https://github.com/openthread/openthread/compare/6f909a1d6a9213cb137615af205aa29e1aca39b1...2caf6b818acb8aeb75f8daa0fa22646d9afd65b0)

---
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 6f909a1..2caf6b8 160000
--- a/third_party/openthread/repo
+++ b/third_party/openthread/repo
@@ -1 +1 @@
-Subproject commit 6f909a1d6a9213cb137615af205aa29e1aca39b1
+Subproject commit 2caf6b818acb8aeb75f8daa0fa22646d9afd65b0