Correct syntax in CHANGELOG (#13474)

Non-breakable space was replaced with whitespace.

CHANGELOG.md

@@ -811,7 +811,7 @@ Each of these changes will continue to work as before with a new warning until t
 - `Object.is` is used in a number of places to compare values, which leads to fewer false positives, especially involving `NaN`. In particular, this affects the `shallowCompare` add-on. ([@chicoxyzzy](https://github.com/chicoxyzzy) in [#6132](https://github.com/facebook/react/pull/6132))
 - Add-Ons: ReactPerf no longer instruments adding or removing an event listener because they don’t really touch the DOM due to event delegation. ([@antoaravinth](https://github.com/antoaravinth) in [#5209](https://github.com/facebook/react/pull/5209))
 
-### Other improvements
+### Other improvements
 
 - React now uses `loose-envify` instead of `envify` so it installs fewer transitive dependencies. ([@qerub](https://github.com/qerub) in [#6303](https://github.com/facebook/react/pull/6303))
 - Shallow renderer now exposes `getMountedInstance()`. ([@glenjamin](https://github.com/glenjamin) in [#4918](https://github.com/facebook/react/pull/4918))