Fix config version

This matches Cargo.lock.  I suspect a mismerge in arti!478.

crates/tor-config/Cargo.toml

@@ -28,7 +28,7 @@ tracing = "0.1.18"
 directories = { version = "4", optional = true }
 
 [dev-dependencies]
-config = { version = "0.12.0", default-features = false, features = ["toml"] }
+config = { version = "0.13", default-features = false, features = ["toml"] }
 dirs = "4.0.0"
 rmp-serde = "1"
 serde_json = "1.0.50"