fixing typo

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@1024407 13f79535-47bb-0310-9956-ffa450edef68

WHATSNEW

@@ -146,7 +146,7 @@ Fixed bugs:
    from a resource or string explicitly.
    Bugzilla Report 49587.
 
- * Project#setDefault threw an excpetion when null was passed in as
+ * Project#setDefault threw an exception when null was passed in as
    argument, even though the javadoc says, null is a valid value.
    Bugzilla Report 49803.