t3104: remove shift code in 'test_ls_tree_format'

In t3104-ls-tree-format.sh, There is a legacy 'shift 2' code
and the relevant code block no longer depends on it anymore,
so let's remove it for a small cleanup.

Signed-off-by: Teng Long <dyroneteng@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3104-ls-tree-format.sh

@@ -20,7 +20,6 @@ test_ls_tree_format () {
 	format=$1 &&
 	opts=$2 &&
 	fmtopts=$3 &&
-	shift 2 &&
 
 	test_expect_success "ls-tree '--format=<$format>' is like options '$opts $fmtopts'" '
 		git ls-tree $opts -r HEAD >expect &&