bug#3572: 23.0.94; Typo in docstring of (defun dir-locals-set-directory-class ...)

diff --git i/lisp/files.el w/lisp/files.el
index 4e81b6a..921724d 100644
--- i/lisp/files.el
+++ w/lisp/files.el
@@ -3243,13 +3243,13 @@ Return the new variables list."
 
 (defun dir-locals-set-directory-class (directory class mtime)
   "Declare that the DIRECTORY root is an instance of CLASS.
 DIRECTORY is the name of a directory, a string.
 CLASS is the name of a project class, a symbol.
 MTIME is either the modification time of the directory-local
-variables file that defined this this class, or nil.
+variables file that defined this class, or nil.
 
 When a file beneath DIRECTORY is visited, the mode-specific
 variables from CLASS are applied to the buffer.  The variables
 for a class are defined using `dir-locals-set-class-variables'."
   (setq directory (file-name-as-directory (expand-file-name directory)))
   (unless (assq class dir-locals-class-alist)