Fix variable naming in TestClient by updating DEV_HOST to use underscore instead of hyphen for environment variable retrieval, ensuring consistency with naming conventions.

Author: reeshika-h

src/test/java/com/contentstack/cms/TestClient.java

@@ -22,7 +22,7 @@ public class TestClient {
     public final static String MANAGEMENT_TOKEN = (env.get("managementToken") != null) ? env.get("managementToken")
             : "managementToken99999999";
 
-    public final static String DEV_HOST = (env.get("dev-host") != null) ? env.get("dev-host").trim() : "api.contentstack.io";
+    public final static String DEV_HOST = (env.get("dev_host") != null) ? env.get("dev_host").trim() : "api.contentstack.io";
     public final static String VARIANT_GROUP_UID = (env.get("variantGroupUid") != null) ? env.get("variantGroupUid")
             : "variantGroupUid99999999";
     private static Contentstack instance;