parallel-checkout: drop unused checkout state parameter

The write_pc_item_to_fd() function takes a "struct checkout *state"
parameter, but never uses it. This was true in its introduction in
fa33dd99 (unpack-trees: add basic support for parallel checkout,
2020-09-22). Its caller, write_pc_item(), has already pulled the useful
bits from the state struct into the "path" variable. Let's drop the
useless parameter.
Signed-off-by: NJeff King <peff@peff.net>
Acked-by: Tavares Bernard
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

parallel-checkout.c

@@ -233,7 +233,7 @@ static int reset_fd(int fd, const char *path)
 }
 
 static int write_pc_item_to_fd(struct parallel_checkout_item *pc_item, int fd,
-			       const char *path, struct checkout *state)
+			       const char *path)
 {
 	int ret;
 	struct stream_filter *filter;
@@ -347,7 +347,7 @@ void write_pc_item(struct parallel_checkout_item *pc_item,
 		goto out;
 	}
 
-	if (write_pc_item_to_fd(pc_item, fd, path.buf, state)) {
+	if (write_pc_item_to_fd(pc_item, fd, path.buf)) {
 		/* Error was already reported. */
 		pc_item->status = PC_ITEM_FAILED;
 		goto out;