Bump org.jenkins-ci.plugins:plugin from 4.88 to 5.6 (#143)

Author: dependabot[bot]

pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <groupId>org.jenkins-ci.plugins</groupId>
     <artifactId>plugin</artifactId>
-    <version>5.5</version>
+    <version>5.6</version>
     <relativePath />
   </parent>