Add a missing changelog entry

Author: bbatsov

CHANGELOG.md

@@ -36,6 +36,7 @@
 * Renamed `cider-prompt-save-file-on-load` to `cider-save-file-on-load` and adjust its supported values accordingly (the default now is `'prompt` and `'always-save` is now simply `t`).
 * [#2014](https://github.com/clojure-emacs/cider/pull/2014): Unify the format for `forms-str` and `arglists-str`.
 * [#2027](https://github.com/clojure-emacs/cider/pull/2027): Mark many custom variables relating to `cider-jack-in` as safe.
+* [#2023](https://github.com/clojure-emacs/cider/issues/2023): Make popup-buffer sexp indentation optional.
 
 ### Bugs Fixed