Update httpclient.version to v5.3.1

Author: renovate[bot]

pom.xml

@@ -15,7 +15,7 @@
     <packaging>hpi</packaging>
 
     <properties>
-        <httpclient.version>5.3</httpclient.version>
+        <httpclient.version>5.3.1</httpclient.version>
         <httpcore.version>5.2.4</httpcore.version>
 
         <revision>${httpclient.version}</revision>