man/man2/mount_setattr.2: Document glibc >= 2.36 syscall wrappers

man/man2/mount_setattr.2: Document glibc >= 2.36 syscall wrappers

glibc 2.36 added syscall wrappers for the entire family of fd-based
mount syscalls, including mount_setattr(2).  Thus it's no longer
necessary to instruct users to do raw syscall(2) operations.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Cc: <linux-api@vger.kernel.org>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: <linux-kernel@vger.kernel.org>
Cc: "Michael T. Kerrisk" <mtk.manpages@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jan Kara <jack@suse.cz>
Cc: Askar Safin <safinaskar@zohomail.com>
Cc: "G. Branden Robinson" <branden@debian.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Message-ID: <20250807-new-mount-api-v2-1-558a27b8068c@cyphar.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>