Bump third_party/libsbp from 84f224f to c7ea9b5

Bumps [third_party/libsbp](https://github.com/swift-nav/libsbp) from `84f224f` to `c7ea9b5`.
- [Release notes](https://github.com/swift-nav/libsbp/releases)
- [Commits](swift-nav/libsbp@84f224f...c7ea9b5)

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

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