completion; remove unuseful comments

The only caller, __git_complete_index_file() doesn't specify any limits
to the options for 'git ls-files', neither should this function.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Felipe Contreras

contrib/completion/git-completion.bash

@@ -323,8 +323,6 @@ __git_diff_index_helper ()
 
 # __git_index_files accepts 1 or 2 arguments:
 # 1: Options to pass to ls-files (required).
-#    Supported options are --cached, --modified, --deleted, --others,
-#    and --directory.
 # 2: A directory path (optional).
 #    If provided, only files within the specified directory are listed.
 #    Sub directories are never recursed.  Path must have a trailing