[1.2.X] Fixed #14846 -- Corrected a tiny typo in from [14832]. Thanks…

… to elbarto for catching the mistake.

Backport of [14846] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14847 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/ref/files/storage.txt

@@ -79,7 +79,7 @@ The Storage Class
 
         Lists the contents of the specified path, returning a 2-tuple of lists;
         the first item being directories, the second item being files. For
-        storage systems that aren't ale to provide such a listing, this will
+        storage systems that aren't able to provide such a listing, this will
         raise a ``NotImplementedError`` instead.
 
     .. method:: open(name, mode='rb')