fix: samples/client/petstore/java/vertx-no-nullable/pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-15907551

Author: snyk-bot

samples/client/petstore/java/vertx-no-nullable/pom.xml

@@ -265,8 +265,8 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <vertx-version>3.5.2</vertx-version>
-        <jackson-version>2.19.2</jackson-version>
-        <jackson-databind>2.19.2</jackson-databind>
+        <jackson-version>2.21.2</jackson-version>
+        <jackson-databind>2.21.2</jackson-databind>
         <jackson-databind-nullable-version>0.2.7</jackson-databind-nullable-version>
         <jakarta-annotation-version>1.3.5</jakarta-annotation-version>
         <junit-version>5.10.3</junit-version>