docs: replace example TURN secret with placeholder

Committed a generated hex string that looked like a real secret.
Replaced with YOUR_SECRET_HERE to make it obviously an example.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -104,7 +104,7 @@ apt install coturn
 listening-port=3478
 fingerprint
 use-auth-secret
-static-auth-secret=b06c504fd091d23c1ae3699337259d7883a0af1c72fe782044de19f314a267aa
+static-auth-secret=YOUR_SECRET_HERE
 realm=your-domain.com
 no-tcp-relay
 ```
@@ -128,7 +128,7 @@ systemctl start coturn
 window.WASTE_CONFIG = {
   signalURL: 'wss://your-domain.com/ws',
   turnURL: 'turn:your-domain.com:3478',
-  turnSecret: 'b06c504fd091d23c1ae3699337259d7883a0af1c72fe782044de19f314a267aa',
+  turnSecret: 'YOUR_SECRET_HERE',
 }
 ```