chore(deps): bump yamux to 0.14

No code changes required. Connection::new, Config::default, Mode::Server
and poll_next_inbound as used by the synthetics tunnel multiplexer are
unchanged in 0.14.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: platinummonkey

Cargo.lock

@@ -124,7 +124,7 @@ aes-gcm = { version = "0.11", optional = true }
 
 # Synthetics tunnel
 tokio-tungstenite = { version = "0.29", features = ["rustls-tls-native-roots"], optional = true }
-yamux = { version = "0.13", optional = true }
+yamux = { version = "0.14", optional = true }
 russh = { version = "0.61", optional = true }
 ssh-key = { version = "0.6", features = ["p256", "std"], optional = true }
 futures = { version = "0.3", optional = true }