fix: samples/client/petstore/java/vertx/pom.xml to reduce vulnerabili…

…ties

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-IONETTY-6056419

samples/client/petstore/java/vertx/pom.xml

@@ -274,7 +274,7 @@
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <vertx-version>3.4.2</vertx-version>
+        <vertx-version>3.9.0</vertx-version>
         <swagger-annotations-version>1.5.22</swagger-annotations-version>
         <jackson-version>2.10.5</jackson-version>
         <jackson-databind>2.10.5.1</jackson-databind>