Remove unused imports in mongodb plugin tests

Signed-off-by: Dinu John <86094133+dinujoh@users.noreply.github.com>

Author: dinujoh

data-prepper-plugins/mongodb/src/test/java/org/opensearch/dataprepper/plugins/mongo/stream/StreamSchedulerTest.java

@@ -1,7 +1,6 @@
 package org.opensearch.dataprepper.plugins.mongo.stream;
 
 import com.mongodb.MongoSecurityException;
-import org.bson.BsonDocument;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;