fix: samples/server/petstore/jaxrs-datelib-j8/pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMGOOGLEGUAVA-5710356

Author: snyk-bot

samples/server/petstore/jaxrs-datelib-j8/pom.xml

@@ -203,7 +203,7 @@ for this project used jakarta.validation-api -->
     <java.version>1.8</java.version>
     <maven.compiler.source>${java.version}</maven.compiler.source>
     <maven.compiler.target>${java.version}</maven.compiler.target>
-    <swagger-core-version>1.6.5</swagger-core-version>
+    <swagger-core-version>1.6.12</swagger-core-version>
     <beanvalidation-version>2.0.2</beanvalidation-version>
     <jetty-version>9.2.9.v20150224</jetty-version>
     <jersey2-version>2.35</jersey2-version>