remove public keyword from default api

Author: Benjosh95

templates/java/api.mustache

@@ -56,7 +56,7 @@ import cloud.stackit.sdk.core.config.CoreConfiguration;
 import cloud.stackit.sdk.core.exception.ApiException;
 
 {{#operations}}
-public class {{classname}} {
+class {{classname}} {
     private ApiClient localVarApiClient;
     private int localHostIndex;
     private String localCustomBaseUrl;