Update CHANGELOG for PR #5151

Author: ponylang-main

CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to the Pony compiler and standard library will be documented
 - Fix rare silent connection hangs on Linux ([PR #5131](https://github.com/ponylang/ponyc/pull/5131))
 - Fix bug in pony-lsp's goto definition ([PR #5123](https://github.com/ponylang/ponyc/pull/5123))
 - Fix pony-lsp failures with some code constructs ([PR #5144](https://github.com/ponylang/ponyc/pull/5144))
+- Fix silent timer hangs on Linux ([PR #5151](https://github.com/ponylang/ponyc/pull/5151))
 
 ### Added