Fix changelog (#234)

Author: nicolas-grekas

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Change Log
 
-## 1.17.0 - 2023-XX-XX
+## 1.17.0 - 2023-04-26
 
 - [#230](https://github.com/php-http/discovery/pull/230) - Add Psr18Client to make it straightforward to use PSR-18
 - [#232](https://github.com/php-http/discovery/pull/232) - Allow pinning the preferred implementations in composer.json