Update dependency org.jenkins-ci.plugins:artifactory to v3.18.8

Author: renovate[bot]

integrations/pom.xml

@@ -164,7 +164,7 @@
     <dependency>
       <groupId>org.jenkins-ci.plugins</groupId>
       <artifactId>artifactory</artifactId>
-      <version>3.18.6</version>
+      <version>3.18.8</version>
       <scope>test</scope>
       <exclusions>
         <!-- RequireUpperBoundDeps with apache-httpcomponents-client-4-api plugin -->