fix(config): remove type annotation on getClient for backwards compat

- keep phpdoc in place for type hints

Author: tharropoulos

src/Lib/Configuration.php

@@ -235,7 +235,7 @@ public function getLogger(): LoggerInterface
     /**
      * @return ClientInterface | HttpMethodsClient
      */
-    public function getClient(): ClientInterface | HttpMethodsClient
+    public function getClient()
     {
         if ($this->client === null) {
             $discoveredClient = Psr18ClientDiscovery::find();