submodule: bump openthread from 7048835 to bd47a31

Bumps [openthread](https://github.com/openthread/openthread) from `7048835` to `bd47a31`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@7048835...bd47a31)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: bd47a31674886543472aacdf7eba3978fad73350
  dependency-type: direct:production
...

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

Author: dependabot[bot]