chore: remove warning from README (#23)

Author: edodusi

README.md

@@ -4,9 +4,6 @@
     <p align="center">Co-created with <a href="https://sensiolabs.com/">SensioLabs</a>, the creators of Symfony.</p>
 </div>
 
-> [!WARNING]
-> This library is in the initial phase and subject to change in a future release.
-
 | Branch    | PHP                                         | Code Coverage                                                                                                                                  |
 |-----------|---------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------|
 | `master`  | [![PHP](https://github.com/storyblok/php-content-api-client/actions/workflows/ci.yaml/badge.svg)](https://github.com/storyblok/php-content-api-client/actions/workflows/ci.yaml)  | [![codecov](https://codecov.io/gh/storyblok/php-content-api-client/graph/badge.svg)](https://codecov.io/gh/storyblok/php-content-api-client) |