hgignore.5: fix typo

hgignore.5: fix typo

--- a/doc/hgignore.5.txt	Wed Nov 11 21:16:20 2009 +0100
+++ b/doc/hgignore.5.txt	Wed Nov 11 21:29:35 2009 +0100
@@ -33,7 +33,7 @@
 root directory, or any prefix path of that path, is matched against
 any pattern in ``.hgignore``.
 
-For example, say we have an an untracked file, ``file.c``, at
+For example, say we have an untracked file, ``file.c``, at
 ``a/b/file.c`` inside our repository. Mercurial will ignore ``file.c``
 if any pattern in ``.hgignore`` matches ``a/b/file.c``, ``a/b`` or ``a``.