ipv6: Document that max_size sysctl is deprecated

mainline inclusion
from mainline-v6.3-rc1
commit 695a376b
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I8ZGOZ
CVE: CVE-2023-52340

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=695a376b59f72c249caad40da64d5cce239c5f48



--------------------------------

v4: fix deprecated typo.

Document that max_size is deprecated due to:

commit af6d1034 ("ipv6: remove max_size check inline with ipv4")

Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com>
Link: https://lore.kernel.org/r/20230120232331.1273881-1-jmaxwell37@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Conflicts:
	Documentation/networking/ip-sysctl.txt
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>