[MASSEMBLY-858] don't declare m-assembly-p as extension: this is not normal use, is not useful (and caused failure when MNG-6209 was fixed)
this shows that MNG-6209 won't break every build with previous m-assembl-p versions: only builds that declare this plugin as extension, but who does that?

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1798339 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/it/it-project-parent/pom.xml b/src/it/it-project-parent/pom.xml
index 5dbbc0d..144de8c 100644
--- a/src/it/it-project-parent/pom.xml
+++ b/src/it/it-project-parent/pom.xml
@@ -70,7 +70,6 @@
           <plugin>
             <artifactId>maven-assembly-plugin</artifactId>
             <version>${testVersion}</version>
-            <extensions>true</extensions>
           </plugin>
           <plugin>
              <artifactId>maven-jar-plugin</artifactId>