fix description of length parameter

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@5706 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_readfile.c

@@ -34,7 +34,7 @@ static char *readfile_descrip =
 "ReadFile(varname=file,length)\n"
 "  Varname - Result stored here.\n"
 "  File - The name of the file to read.\n"
-"  Length   - Maximum number of lines to capture.\n";
+"  Length - Maximum number of characters to capture.\n";
 
 STANDARD_LOCAL_USER;