[Bug #990524] Fix typo

Doc/mac/undoc.tex

@@ -73,7 +73,7 @@ dialogs and menus, without requiring special case code for when the
 script is run under MacPython, as a MacPython applet or under OSX Python.
 
 \section{\module{Nav} --- NavServices calls}
-\declaremodule{standard}{Nac}
+\declaremodule{standard}{Nav}
   \platform{Mac}
 \modulesynopsis{Interface to Navigation Services.}