ipv6: Document that max_size sysctl is deprecated

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: NJon Maxwell <jmaxwell37@gmail.com>
Link: https://lore.kernel.org/r/20230120232331.1273881-1-jmaxwell37@gmail.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

Documentation/networking/ip-sysctl.rst

@@ -156,6 +156,9 @@ route/max_size - INTEGER
 	From linux kernel 3.6 onwards, this is deprecated for ipv4
 	as route cache is no longer used.
 
+	From linux kernel 6.3 onwards, this is deprecated for ipv6
+	as garbage collection manages cached route entries.
+
 neigh/default/gc_thresh1 - INTEGER
 	Minimum number of entries to keep.  Garbage collector will not
 	purge entries if there are fewer than this number.