chore(deps): update dependency io.vertx:vertx-core to v3.8.4 (#1857)
chore(deps): update dependency io.vertx:vertx-core to v3.8.4 (#1857)


GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples