deps: update dependency io.grpc:grpc-testing to v1.30.0 (#119)

Author: renovate-bot

pubsublite-beam-io/pom.xml

@@ -116,7 +116,7 @@
     <dependency>
       <groupId>io.grpc</groupId>
       <artifactId>grpc-testing</artifactId>
-      <version>1.29.0</version>
+      <version>1.30.0</version>
       <scope>test</scope>
     </dependency>
     <dependency>