Minor IPv6 security group improvements in v3 doc (#4534)

- mention cc.enable_ipv6
- leading zeros are forbidden in IPv4 destinations only but allowed for IPv6

Author: stephanme

docs/v3/source/includes/resources/security_groups/_header.md

@@ -5,3 +5,5 @@ Security groups are collections of egress traffic rules that can be applied to t
 Security groups can either be applied globally or at the space-level.
 
 Security groups can only allow (whitelist) traffic. They cannot be used to disallow (blacklist) traffic.
+
+IPv6 security groups can be configured if `cc.enable_ipv6` is set to `true`.

docs/v3/source/includes/resources/security_groups/_object.md.erb

@@ -26,7 +26,7 @@ Name | Type | Description
 | Name | Type | Description | Required | Default
 | ---- | ---- | ----------- | -------- | -------
 | **protocol** | _string_ | Protocol type Valid values are `tcp`, `udp`, `icmp`, `icmpv6` or `all` | yes | N/A |
-| **destination** | _string_ | The destination where the rule applies. Must be a singular valid CIDR, IP address, or IP address range unless `cc.security_groups.enable_comma_delimited_destinations` is enabled. Then, the destination can be a comma-delimited string of CIDRs, IP addresses, or IP address ranges. Octets within destinations cannot contain leading zeros; eg. `10.0.0.0/24` is valid, but `010.00.000.0/24` is *not*. For `icmp`, only IPv4 addresses are allowed and for `icmpv6` only IPv6 addresses. | yes | N/A |
+| **destination** | _string_ | The destination where the rule applies. Must be a singular valid CIDR, IP address, or IP address range unless `cc.security_groups.enable_comma_delimited_destinations` is enabled. Then, the destination can be a comma-delimited string of CIDRs, IP addresses, or IP address ranges. Octets within IPv4 destinations cannot contain leading zeros; eg. `10.0.0.0/24` is valid, but `010.00.000.0/24` is *not*. For `icmp`, only IPv4 addresses are allowed and for `icmpv6` only IPv6 addresses. | yes | N/A |
 | **ports** | _string_ | Ports that the rule applies to; can be a single port (`9000`), a comma-separated list (`9000,9001`), or a range (`9000-9200`) | no | `null` |
 | **type** | _integer_ |[Type](https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml#icmp-parameters-types) required for ICMP protocol; valid values are between -1 and 255 (inclusive), where -1 allows all | no | `null` |
 | **code** | _integer_ |[Code](https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml#icmp-parameters-codes) required for ICMP protocol; valid values are between -1 and 255 (inclusive), where -1 allows all | no | `null` |