Use plugin pom 5.7

https://github.com/jenkinsci/plugin-pom/releases/tag/plugin-5.7

Author: MarkEWaite

pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <groupId>org.jenkins-ci.plugins</groupId>
     <artifactId>plugin</artifactId>
-    <version>5.6</version>
+    <version>5.7</version>
     <relativePath />
   </parent>