chore: prepare v0.22.3 (#209)

Signed-off-by: Max Inden <mail@max-inden.de>

CHANGELOG.md

@@ -4,13 +4,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [0.22.3] - unreleased
+## [0.22.3]
 
 ### Added
 
 - Added `encode_registry` and `encode_eof` functions to `text` module.
   See [PR 205].
-  
+
   [PR 205]: https://github.com/prometheus/client_rust/pull/205
 
 - Support all platforms with 32 bit atomics lacking 64 bit atomics.