Add that some names are reserved with ghe.com (#60585)

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: mc <42146119+mchammer01@users.noreply.github.com>

Author: 3 people

content/admin/data-residency/feature-overview-for-github-enterprise-cloud-with-data-residency.md

@@ -47,6 +47,7 @@ The following features are either specific to {% data variables.enterprise.data_
 
 * [API access](#api-access)
 * [URL differences](#url-differences)
+* [Organization names and usernames](#organization-names-and-usernames)
 * [{% data variables.product.prodname_actions %} workflows from {% data variables.product.prodname_marketplace %}](#github-actions-workflows-from-github-marketplace)
 * [Retirement of namespaces for actions accessed on {% data variables.product.prodname_dotcom_the_website %}](#retirement-of-namespaces-for-actions-accessed-on-githubcom)
 * [GitHub Connect](#github-connect)
@@ -75,6 +76,10 @@ The following examples are not exhaustive.
 
 {% endrowheaders %}
 
+### Organization names and usernames
+
+{% data variables.enterprise.data_residency_site %} reserves certain usernames and organization names for internal use. If you try to create a user or organization with one of these names, you'll get an error stating the name is unavailable.
+
 ### {% data variables.product.prodname_actions %} workflows from {% data variables.product.prodname_marketplace %}
 
 {% data variables.product.prodname_actions %} workflows from the {% data variables.product.prodname_marketplace %} may not work as users expect.