Fix typo - remove duplicate characters

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1661662 13f79535-47bb-0310-9956-ffa450edef68

build.xml

@@ -579,7 +579,7 @@ under the License.
                     <available file="${ooxml.xsds.jar}"/>
                     <available file="${ooxml.security.jar}"/>
                     <available file="${ooxml.xsds.src.jar}"/>
-                    <available file="${${ooxml.security.src.jar}"/>
+                    <available file="${ooxml.security.src.jar}"/>
             	</and>
                 <isset property="disconnected"/>
             </or>