chore(iroh): Update portmapper (#3410)

## Description

This avoids a double-dependency on n0-watcher versions 0.2 and 0.3. I
accidentally didn't push this to #3405

## Change checklist
<!-- Remove any that are not relevant. -->
- [x] Self-review.

Author: matheus23

Cargo.lock

@@ -108,7 +108,7 @@ parse-size = { version = "=1.0.0", optional = true, features = ['std'] } # pinne
 hickory-resolver = "0.25.1"
 igd-next = { version = "0.16", features = ["aio_tokio"] }
 netdev = { version = "0.36.0" }
-portmapper = { version = "0.7", default-features = false }
+portmapper = { version = "0.8", default-features = false }
 quinn = { package = "iroh-quinn", version = "0.14.0", default-features = false, features = ["runtime-tokio", "rustls-ring"] }
 tokio = { version = "1", features = [
     "io-util",