Bump tunnel-agent from 0.4.3 to 0.6.0

Bumps [tunnel-agent](https://github.com/mikeal/tunnel-agent) from 0.4.3 to 0.6.0.
- [Release notes](https://github.com/mikeal/tunnel-agent/releases)
- [Commits](request/tunnel-agent@v0.4.3...v0.6.0)

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

Author: dependabot[bot]