Documentation: remove backslashes in manpage synopses

For some reason, various manual pages have an asterisk escaped
with \ in the synopsis.  Since there is no other asterisk to pair it
with, Asciidoc does not consider this asterisk escapable, so it passes
the backslash through.

Each page either uses [verse] or has only one asterisk, so it
is safe to drop the backslashes (checked with asciidoc 8.5.2).

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-checkout-index.txt

@@ -13,7 +13,7 @@ SYNOPSIS
 		   [--stage=<number>|all]
 		   [--temp]
 		   [-z] [--stdin]
-		   [--] [<file>]\*
+		   [--] [<file>]*
 
 DESCRIPTION
 -----------

Documentation/git-commit-tree.txt

@@ -8,7 +8,7 @@ git-commit-tree - Create a new commit object
 
 SYNOPSIS
 --------
-'git commit-tree' <tree> [-p <parent commit>]\* < changelog
+'git commit-tree' <tree> [-p <parent commit>]* < changelog
 
 DESCRIPTION
 -----------

Documentation/git-for-each-ref.txt

@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git for-each-ref' [--count=<count>] [--shell|--perl|--python|--tcl]
-		   [--sort=<key>]\* [--format=<format>] [<pattern>...]
+		   [--sort=<key>]* [--format=<format>] [<pattern>...]
 
 DESCRIPTION
 -----------

Documentation/git-ls-files.txt

@@ -10,14 +10,14 @@ SYNOPSIS
 --------
 [verse]
 'git ls-files' [-z] [-t] [-v]
-		(--[cached|deleted|others|ignored|stage|unmerged|killed|modified])\*
-		(-[c|d|o|i|s|u|k|m])\*
+		(--[cached|deleted|others|ignored|stage|unmerged|killed|modified])*
+		(-[c|d|o|i|s|u|k|m])*
 		[-x <pattern>|--exclude=<pattern>]
 		[-X <file>|--exclude-from=<file>]
 		[--exclude-per-directory=<file>]
 		[--exclude-standard]
 		[--error-unmatch] [--with-tree=<tree-ish>]
-		[--full-name] [--abbrev] [--] [<file>]\*
+		[--full-name] [--abbrev] [--] [<file>]*
 
 DESCRIPTION
 -----------

Documentation/git-merge-index.txt

@@ -8,7 +8,7 @@ git-merge-index - Run a merge for files needing merging
 
 SYNOPSIS
 --------
-'git merge-index' [-o] [-q] <merge-program> (-a | [--] <file>\*)
+'git merge-index' [-o] [-q] <merge-program> (-a | [--] <file>*)
 
 DESCRIPTION
 -----------

Documentation/git-relink.txt

@@ -7,7 +7,7 @@ git-relink - Hardlink common objects in local repositories
 
 SYNOPSIS
 --------
-'git relink' [--safe] <dir> [<dir>]\* <master_dir>
+'git relink' [--safe] <dir> [<dir>]* <master_dir>
 
 DESCRIPTION
 -----------

Documentation/git-update-index.txt

@@ -12,7 +12,7 @@ SYNOPSIS
 'git update-index'
 	     [--add] [--remove | --force-remove] [--replace]
 	     [--refresh] [-q] [--unmerged] [--ignore-missing]
-	     [--cacheinfo <mode> <object> <file>]\*
+	     [--cacheinfo <mode> <object> <file>]*
 	     [--chmod=(+|-)x]
 	     [--assume-unchanged | --no-assume-unchanged]
 	     [--skip-worktree | --no-skip-worktree]
@@ -21,7 +21,7 @@ SYNOPSIS
 	     [--info-only] [--index-info]
 	     [-z] [--stdin]
 	     [--verbose]
-	     [--] [<file>]\*
+	     [--] [<file>]*
 
 DESCRIPTION
 -----------