Bump tracing from 0.1.38 to 0.1.40 in /sources/pavex/examples/skeleton

Bumps [tracing](https://github.com/tokio-rs/tracing) from 0.1.38 to 0.1.40.
- [Release notes](https://github.com/tokio-rs/tracing/releases)
- [Commits](tokio-rs/tracing@tracing-0.1.38...tracing-0.1.40)

---
updated-dependencies:
- dependency-name: tracing
  dependency-type: indirect
...

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