Fix Platform.sh deploy URL

Author: fabpot

README.md

@@ -42,7 +42,7 @@ $ composer install
 the official Symfony PaaS, so you can try it without installing anything locally:
 
 <p align="center">
-<a href="https://console.platform.sh/projects/create-project?template=https://raw.githubusercontent.com/symfonycorp/platformsh-symfony-template-metadata/main/template-metadata-demo.yaml&utm_content=symfonycorp&utm_source=github&utm_medium=button&utm_campaign=deploy_on_platform"><img src="https://platform.sh/images/deploy/lg-blue.svg" alt="Deploy on Platform.sh" width="180px" /></a>
+<a href="https://console.platform.sh/projects/create-project?template=https://raw.githubusercontent.com/symfonycorp/platformsh-symfony-template-metadata/main/symfony-demo.template.yaml&utm_content=symfonycorp&utm_source=github&utm_medium=button&utm_campaign=deploy_on_platform"><img src="https://platform.sh/images/deploy/lg-blue.svg" alt="Deploy on Platform.sh" width="180px" /></a>
 </p>
 
 Usage