doc: use three dots for indicating repetition instead of star

This is how it is specified in CodingGuidelines.

Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-fsck.txt

@@ -12,7 +12,7 @@ SYNOPSIS
 'git fsck' [--tags] [--root] [--unreachable] [--cache] [--no-reflogs]
 	 [--[no-]full] [--strict] [--verbose] [--lost-found]
 	 [--[no-]dangling] [--[no-]progress] [--connectivity-only]
-	 [--[no-]name-objects] [<object>*]
+	 [--[no-]name-objects] [<object>...]
 
 DESCRIPTION
 -----------

Documentation/git-merge-index.txt

@@ -9,7 +9,7 @@ git-merge-index - Run a merge for files needing merging
 SYNOPSIS
 --------
 [verse]
-'git merge-index' [-o] [-q] <merge-program> (-a | [--] <file>*)
+'git merge-index' [-o] [-q] <merge-program> (-a | ( [--] <file>...) )
 
 DESCRIPTION
 -----------