Update rcgen requirement from 0.12 to 0.13

Updates the requirements on [rcgen](https://github.com/rustls/rcgen) to permit the latest version.
- [Commits](rustls/rcgen@v0.12.0...v0.13.0)

---
updated-dependencies:
- dependency-name: rcgen
  dependency-type: direct:production
...

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

Cargo.toml

@@ -24,6 +24,6 @@ tokio = "1"
 [dev-dependencies]
 futures = "0.3"
 lazy_static = "1"
-rcgen = "0.12"
+rcgen = "0.13"
 rustls = "0.21"
 tokio = { version = "1", features = ["macros", "rt", "sync"] }