[Improvement]: Add tenant-specific GHEC URLs to Allowlist reference doc (#58316)

Co-authored-by: Sarita Iyer <[email protected]>

Author: sophietheking

content/copilot/reference/allowlist-reference.md

@@ -35,6 +35,8 @@ If your company employs security measures like a firewall or proxy server, you s
 | `https://*.individual.githubcopilot.com`[^2]                | API service for {% data variables.product.prodname_copilot_short %} suggestions |
 | `https://*.business.githubcopilot.com`[^3]                  | API service for {% data variables.product.prodname_copilot_short %} suggestions |
 | `https://*.enterprise.githubcopilot.com`[^4]                | API service for {% data variables.product.prodname_copilot_short %} suggestions |
+| `https://*.SUBDOMAIN.ghe.com`                                      | For {% data variables.product.prodname_copilot_short %} users on {% data variables.enterprise.data_residency_site %} |
+| `https://SUBDOMAIN.ghe.com`                                        | For {% data variables.product.prodname_copilot_short %} users on {% data variables.enterprise.data_residency_site %} |
 
 Depending on the security policies and editors your organization uses, you may need to allowlist additional domains and URLs. For more information on specific editors, see [Further reading](#further-reading).