review: name the state in the health-hint assert

hbb_common is edition 2018, where a lone string literal is not treated as a
format string, so the capture printed itself and the loop over the two
terminal states could not say which one had failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019aokqJuhjvB3kijXtAg5Ns

src/webrtc.rs

@@ -2285,7 +2285,8 @@ IHR5cCBzcmZseCByYWRkciAwLjAuMC4wIHJwb3J0IDY0MDA4XHJcbmE9ZW5kLW9mLWNhbmRpZGF0ZXNc
             WebRTCStream::note_health(&flag, terminal);
             assert!(
                 flag.load(Ordering::SeqCst),
-                "{terminal} must leave the hint as it found it"
+                "{} must leave the hint as it found it",
+                terminal
             );
         }
     }