Update changelog

Author: yuhan0

CHANGELOG.md

@@ -4,6 +4,9 @@
 
 ## New features
 
+* [#3188](https://github.com/clojure-emacs/cider/pull/3188): Add support for `undef-all` op, for removing stale vars and conflicting aliases.
+  * Add new command `cider-undef-all`.
+  * Existing commands `cider-load-buffer`, `cider-load-file`, and `cider-eval-ns-form` can be called with `C-u` prefix to execute `undef-all` before reloading the ns.
 * [#3185](https://github.com/clojure-emacs/cider/pull/3185): Add feature to `cider-eval-in-context` for automatically extracting parent let bindings when called with `C-u` prefix argument.
 * Add new interactive command `cider-inspire-me`. It does what you'd expect.
 * [#3162](https://github.com/clojure-emacs/cider/pull/3162): Save eval results into kill ring and registers.