Bump third_party/libdatachannel/repo from 59ce380 to 7f42c7d

Bumps [third_party/libdatachannel/repo](https://github.com/paullouisageneau/libdatachannel) from `59ce380` to `7f42c7d`.
- [Release notes](https://github.com/paullouisageneau/libdatachannel/releases)
- [Commits](paullouisageneau/libdatachannel@59ce380...7f42c7d)

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

Signed-off-by: dependabot[bot] <[email protected]>