Removing unused code

Author: sashirestela

src/main/java/io/github/sashirestela/openai/base/RealtimeConfig.java

@@ -20,8 +20,4 @@ public static RealtimeConfig of(String model) {
         return new RealtimeConfig(model, null, null, null);
     }
 
-    public static RealtimeConfig of(String model, String endpointUrl) {
-        return new RealtimeConfig(model, endpointUrl, null, null);
-    }
-
 }