Upgrade org.codehaus.plexus:plexus-component-metadata to 1.7.1
This will make them build with Java9

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@1772107 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 05bc438..8038e7b 100644
--- a/pom.xml
+++ b/pom.xml
@@ -107,7 +107,7 @@
         <!--
           ! Can be removed if update to maven-shared-components parent to version 31
         -->
-        <version>1.7</version>
+        <version>1.7.1</version>
         <executions>
           <execution>
             <id>create-component-descriptor</id>