Set parent pom version to the recommended one

Author: Antonio Mansilla

pom.xml

@@ -5,9 +5,7 @@
   <parent>
     <groupId>org.jenkins-ci.plugins</groupId>
     <artifactId>plugin</artifactId>
-    <!-- Baseline Jenkins version you use to build and test the plugin. Users must have this version or newer to run. -->
-    <version>1.609.1</version>
-    <relativePath />
+    <version>2.21</version>
   </parent>
 
   <groupId>org.jenkins-ci.plugins</groupId>
@@ -26,6 +24,7 @@
   <name>Bitbucket Build Status Notifier Plugin</name>
   <description>Integrates Jenkins build status with BitBucket</description>
   <url>https://wiki.jenkins-ci.org/display/JENKINS/Bitbucket+Cloud+Build+Status+Notifier+Plugin</url>
+
   <licenses>
     <license>
       <name>MIT License</name>