upgrade to last parent version 15

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@907518 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 1300621..8f784d8 100644
--- a/pom.xml
+++ b/pom.xml
@@ -24,7 +24,7 @@
   <parent>
     <groupId>org.apache.maven.shared</groupId>
     <artifactId>maven-shared-components</artifactId>
-    <version>12</version>
+    <version>15</version>
   </parent>
 
   <artifactId>maven-shared-jar</artifactId>