Removing -n option from git-diff-files documentation

-n is not a short form of --no-index as the documentation
suggests.  Removing it from the documentation and command
usage string.
Signed-off-by: NAndrew Ruder <andy@aeruder.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/git-diff-files.txt

@@ -8,7 +8,7 @@ git-diff-files - Compares files in the working tree and the index
 
 SYNOPSIS
 --------
-'git-diff-files' [-q] [-0|-1|-2|-3|-c|--cc|-n|--no-index] [<common diff options>] [<path>...]
+'git-diff-files' [-q] [-0|-1|-2|-3|-c|--cc|--no-index] [<common diff options>] [<path>...]
 
 DESCRIPTION
 -----------
@@ -36,7 +36,7 @@ omit diff output for unmerged entries and just show "Unmerged".
 	diff, similar to the way 'diff-tree' shows a merge
 	commit with these flags.
 
-\-n,\--no-index::
+--no-index::
 	Compare the two given files / directories.
 
 -q::

builtin-diff-files.c

@@ -10,7 +10,7 @@
 #include "builtin.h"
 
 static const char diff_files_usage[] =
-"git-diff-files [-q] [-0/-1/2/3 |-c|--cc|-n|--no-index] [<common diff options>] [<path>...]"
+"git-diff-files [-q] [-0/-1/2/3 |-c|--cc|--no-index] [<common diff options>] [<path>...]"
 COMMON_DIFF_OPTIONS_HELP;
 
 int cmd_diff_files(int argc, const char **argv, const char *prefix)