Add copyright comment

Author: whuffman36

google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/OpenTelemetryHelper.java

@@ -1,13 +1,27 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * 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 com.google.cloud.bigquery;
 
 import com.google.api.core.InternalApi;
 import com.google.api.services.bigquery.model.QueryRequest;
 import com.google.cloud.Policy;
-import com.google.cloud.bigquery.BigQuery.IAMOption;
 import com.google.cloud.bigquery.spi.v2.BigQueryRpc;
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.api.trace.Tracer;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;