Bump third_party/libsbp from b9860dc to 9415861

Bumps [third_party/libsbp](https://github.com/swift-nav/libsbp) from `b9860dc` to `9415861`.
- [Release notes](https://github.com/swift-nav/libsbp/releases)
- [Commits](swift-nav/libsbp@b9860dc...9415861)

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

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