Use parent pom 3.54

Includes imnprovements in the Jenkins test harness

Author: MarkEWaite

pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <groupId>org.jenkins-ci.plugins</groupId>
     <artifactId>plugin</artifactId>
-    <version>3.50</version>
+    <version>3.54</version>
     <relativePath />
   </parent>