fix: samples/client/petstore/scala-akka/pom.xml to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-COMFASTERXMLJACKSONCORE-10500754

Author: snyk-bot

samples/client/petstore/scala-akka/pom.xml

@@ -16,7 +16,7 @@
 
     <java.version>1.8</java.version>
     <scala.version>2.12.13</scala.version>
-    <json4s.jackson.version>3.6.7</json4s.jackson.version>
+    <json4s.jackson.version>4.0.0</json4s.jackson.version>
     <json4s.ext.version>3.6.7</json4s.ext.version>
     <akka.version>2.6.12</akka.version>
     <akka.http.version>10.2.3</akka.http.version>