Revert last change because I am a doppy bugger

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@272153 13f79535-47bb-0310-9956-ffa450edef68

build.xml

@@ -574,7 +574,7 @@
       <manifest>
         <section name="${ant.package}">
           <attribute name="Extension-name"
-                     value="${ant.package}" />
+                     value="org.apache.tools.ant" />
           <attribute name="Specification-Title"
                      value="Apache Ant" />
           <attribute name="Specification-Version"