fix test

Change-Id: Iad72d2a9d012938f24c0ad91876effbbf67a853c

Author: igorbernstein2

google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/data/v2/internal/api/ClientTest.java

@@ -55,10 +55,7 @@
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.ExtendWith;
-import org.mockito.junit.jupiter.MockitoExtension;
 
-@ExtendWith(MockitoExtension.class)
 public class ClientTest {
   private ClientConfiguration defaultConfig;