zdb: Add missing poolname to -C synopsis

Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Reviewed-by: Rob Norris <robn@despairlabs.com>
Signed-off-by: Mateusz Piotrowski <0mp@FreeBSD.org>
Sponsored-by: Klara Inc.
Closes #15014

cmd/zdb/zdb.c

@@ -794,7 +794,7 @@ usage(void)
 	    "\t\t[-o <var>=<value>]... [-t <txg>] [-U <cache>] [-x <dumpdir>]\n"
 	    "\t\t[-K <key>] <poolname>/<objset id> [<backupflags>]\n"
 	    "\t%s [-v] <bookmark>\n"
-	    "\t%s -C [-A] [-U <cache>]\n"
+	    "\t%s -C [-A] [-U <cache>] [<poolname>]\n"
 	    "\t%s -l [-Aqu] <device>\n"
 	    "\t%s -m [-AFLPX] [-e [-V] [-p <path> ...]] [-t <txg>] "
 	    "[-U <cache>]\n\t\t<poolname> [<vdev> [<metaslab> ...]]\n"

man/man8/zdb.8

@@ -14,7 +14,7 @@
 .\" Copyright (c) 2017 Lawrence Livermore National Security, LLC.
 .\" Copyright (c) 2017 Intel Corporation.
 .\"
-.Dd June 4, 2023
+.Dd June 27, 2023
 .Dt ZDB 8
 .Os
 .
@@ -51,6 +51,7 @@
 .Fl C
 .Op Fl A
 .Op Fl U Ar cache
+.Op Ar poolname
 .Nm
 .Fl E
 .Op Fl A