upgrade plugins to latest parent 21


git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1153134 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 0255b65..e1984a4 100644
--- a/pom.xml
+++ b/pom.xml
@@ -25,7 +25,7 @@
   <parent>
     <artifactId>maven-plugins</artifactId>
     <groupId>org.apache.maven.plugins</groupId>
-    <version>20</version>
+    <version>21</version>
     <relativePath>../maven-plugins/pom.xml</relativePath>
   </parent>