fix: samples/client/echo_api/java/resteasy/pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMSUNMAIL-12028709

Author: snyk-bot

samples/client/echo_api/java/resteasy/pom.xml

@@ -253,7 +253,7 @@
     </dependencies>
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <resteasy-version>4.7.6.Final</resteasy-version>
+        <resteasy-version>6.1.0.Final</resteasy-version>
         <jackson-version>2.17.1</jackson-version>
         <jackson-databind-version>2.17.1</jackson-databind-version>
         <jackson-databind-nullable-version>0.2.6</jackson-databind-nullable-version>