Fixed typing error.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@1071420 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/util/FileNameMapper.java

@@ -53,7 +53,7 @@ public interface FileNameMapper {
      *
      * @param sourceFileName the name of the source file relative to
      *                       some given basedirectory.
-     * @return an array of strings if the ruld applies to the source file, or
+     * @return an array of strings if the rule applies to the source file, or
      *         null if it does not.
      */
     String[] mapFileName(String sourceFileName);