submodule: bump openthread from d015004 to 74645c0

Bumps [openthread](https://github.com/openthread/openthread) from `d015004` to `74645c0`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@d015004...74645c0)

---
updated-dependencies:
- dependency-name: openthread
  dependency-type: direct:production
...

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