remove invalid relativePath from parent section

This used to point to our 'build pom' when we have been using SVN.
With moving to GIT this is now illegal as we do reference a fixed
parent now.
diff --git a/pom.xml b/pom.xml
index 81df84e..d205a94 100644
--- a/pom.xml
+++ b/pom.xml
@@ -26,7 +26,6 @@
     <artifactId>maven-plugins</artifactId>
     <groupId>org.apache.maven.plugins</groupId>
     <version>33</version>
-    <relativePath>../../pom/maven/maven-plugins/pom.xml</relativePath>
   </parent>
 
   <artifactId>maven-assembly-plugin</artifactId>