use http/1.1 ALPN for WSS listener

[fabracht]

Summary

• WSS listener was enforcing mqtt ALPN, causing browsers to fail TLS handshake with alert 120 (no application protocol) since they offer h2,http/1.1
• Changed WSS TlsAcceptorConfig to advertise http/1.1 ALPN instead of mqtt
• MQTTS listener (port 8883) retains mqtt ALPN unchanged
• Only http/1.1 is offered (not h2) because the broker doesn't implement RFC 8441 — advertising h2 would break Firefox WebSocket connections
• Backfilled missing 0.31.3 changelog entry

Test plan

• test_wss_accepts_http11_alpn — raw TLS handshake with http/1.1 ALPN succeeds
• test_wss_rejects_mqtt_only_alpn — mqtt-only ALPN is rejected (no overlap)
• test_wss_accepts_browser_alpn — browser-style h2,http/1.1 negotiates http/1.1
• Existing TLS integration tests pass (5/5)
• Existing WebSocket integration tests pass (4/4)
• cargo clippy --all-targets --workspace -- -D warnings -W clippy::pedantic clean
• Manual: connect to WSS port from a browser