fix: do not use java.time in jdk7 build
@@ -7,7 +7,7 @@ import io.grpc.Status;
import io.grpc.StatusRuntimeException;
import io.grpc.stub.ClientCalls;
import io.grpc.stub.StreamObserver;
-import java.time.Duration;
+import org.threeten.bp.Duration;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Objects;
