add missing apl2

adapter-milvus/src/main/java/io/nosqlbench/adapter/milvus/opdispensers/MilvusDropCollectionOpDispenser.java

@@ -1,5 +1,23 @@
 package io.nosqlbench.adapter.milvus.opdispensers;
 
+/*
+ * Copyright (c) 2022 nosqlbench
+ * 
+ * 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.
+ */
+
+
 import io.milvus.client.MilvusServiceClient;
 import io.milvus.param.collection.DropCollectionParam;
 import io.nosqlbench.adapter.milvus.MilvusDriverAdapter;