unix/linux: update Dockerfile to Kernel 5.13

Fixes golang/go#47057

Change-Id: I47bc7491ed46afd76d4955c2843f2bb1295c672b
Reviewed-on: https://go-review.googlesource.com/c/sys/+/332969
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/zsysnum_linux_386.go b/unix/zsysnum_linux_386.go
index fbc59b7..eb3afe6 100644
--- a/unix/zsysnum_linux_386.go
+++ b/unix/zsysnum_linux_386.go
@@ -439,4 +439,7 @@
 	SYS_PROCESS_MADVISE              = 440
 	SYS_EPOLL_PWAIT2                 = 441
 	SYS_MOUNT_SETATTR                = 442
+	SYS_LANDLOCK_CREATE_RULESET      = 444
+	SYS_LANDLOCK_ADD_RULE            = 445
+	SYS_LANDLOCK_RESTRICT_SELF       = 446
 )