chore(deps): remove mockito-core version override in google-cloud-bigquerystorage (#13807)

Author: lqiu96

java-bigquerystorage/google-cloud-bigquerystorage/pom.xml

@@ -238,7 +238,6 @@
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>
-      <version>3.12.4</version>
       <scope>test</scope>
     </dependency>
     <dependency>