fix typo

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@278476 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/CoreTasks/subant.html

@@ -51,7 +51,7 @@
             This is an extension
             of ant for bulk project execution.
 
-            <strong>This task must no be used outside of a
+            <strong>This task must not be used outside of a
                 <code>target</code> if it invokes the same build file it is
                 part of.</strong>
         </p>