deps: update dependency org.mockito:mockito-core to v3.4.4 (#170)

Author: renovate-bot

google-cloud-nio/pom.xml

@@ -86,7 +86,7 @@
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>
-      <version>3.3.3</version>
+      <version>3.4.4</version>
       <scope>test</scope>
     </dependency><dependency>
       <groupId>org.hamcrest</groupId>