docs: fixed broken link README.md

Author: AnanthaRajuC

README.md

@@ -40,7 +40,7 @@ This is a simple, self-conatined Spring Boot Web Application with REST end point
 - [Installation](documents/INSTALLATION.MD)  
 - [API](documents/API.md)
 - [Docker](documents/DOCKER.md)  
-- [Documentation](documents/DOCUMENTATION.md)  
+- [Documentation](documents/DOCUMENTATION.MD)  
 
 **Note** : This project has been used as an example for the following blog posts.