openvidu-server: Typo. Add missing license comment

openvidu-server/src/main/java/io/openvidu/server/coturn/CoturnCredentialsService.java

@@ -1,3 +1,20 @@
+/*
+ * (C) Copyright 2017-2022 OpenVidu (https://openvidu.io)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
 package io.openvidu.server.coturn;
 
 import io.openvidu.java.client.IceServerProperties;