TUN-8818: update changes document to reflect newly added diag subcommand

Closes TUN-8818

CHANGES.md

@@ -1,3 +1,7 @@
+## 2024.12.2
+### New Features
+- This release introduces the ability to collect troubleshooting information from one instance of cloudflared running on the local machine. The command can be executed as `cloudflared tunnel diag`.
+
 ## 2024.12.1
 ### Notices
 - The use of the `--metrics` is still honoured meaning that if this flag is set the metrics server will try to bind it, however, this version includes a change that makes the metrics server bind to a port with a semi-deterministic approach. If the metrics flag is not present the server will bind to the first available port of the range 20241 to 20245. In case of all ports being unavailable then the fallback is to bind to a random port.