[#22737] Add line about timer support for Go

CHANGES.md

@@ -65,6 +65,7 @@
 * Allow prebuilding large images when using `--prebuild_sdk_container_engine=cloud_build`, like images depending on `tensorflow` or `torch` ([#27023](https://github.com/apache/beam/pull/27023)).
 * Disabled `pip` cache when installing packages on the workers. This reduces the size of prebuilt Python container images ([#27035](https://github.com/apache/beam/pull/27035)).
 * Select dedicated avro datum reader and writer (Java) ([#18874](https://github.com/apache/beam/issues/18874)).
+* Timer API for the Go SDK (Go) ([#22737](https://github.com/apache/beam/issues/22737)).
 
 ## Breaking Changes