Fix hard-coded constructor name of enum class

in Java okhttp-gson client

Author: xhh

modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/enumClass.mustache

@@ -6,7 +6,7 @@ public enum {{datatypeWithEnum}} {
 
   private String value;
 
-  StatusEnum(String value) {
+  {{datatypeWithEnum}}(String value) {
     this.value = value;
   }