[WAF] An IPv6 range in a custom list can only be as large as /12 (#17133)

Author: favonia

src/content/docs/waf/tools/lists/custom-lists.mdx

@@ -56,7 +56,7 @@ List items in custom lists with IP addresses must be in one of the following for
 
 - Individual IPv4 addresses
 - IPv4 CIDR ranges with a prefix from `/8` to `/32`
-- IPv6 CIDR ranges with a prefix from `/4` to `/64`
+- IPv6 CIDR ranges with a prefix from `/12` to `/64`
 
 You can combine individual addresses and CIDR ranges in the same list.