Bump hibernate-validator in /samples/struts2/pet-store (#357)

Bumps [hibernate-validator](https://github.com/hibernate/hibernate-validator) from 4.3.2.Final to 5.3.5.Final.
- [Release notes](https://github.com/hibernate/hibernate-validator/releases)
- [Changelog](https://github.com/hibernate/hibernate-validator/blob/5.3.5.Final/changelog.txt)
- [Commits](hibernate/hibernate-validator@4.3.2.Final...5.3.5.Final)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

samples/struts2/pet-store/pom.xml

@@ -81,7 +81,7 @@
         <dependency>
             <groupId>org.hibernate</groupId>
             <artifactId>hibernate-validator</artifactId>
-            <version>4.3.2.Final</version>
+            <version>5.3.5.Final</version>
         </dependency>
 
         <dependency>