Clarify that content exclusion requires Copilot Business or Enterprise plan

The how-to and concepts pages for content exclusion do not explicitly
state that repository-level content exclusion settings are only available
for repositories owned by an organization with a Copilot Business or
Enterprise plan. Users with personal accounts (Copilot Free, Pro, or
Pro+) cannot find the Copilot settings in their repository and have no
clear explanation why.

This adds:
- A NOTE callout in the how-to page clarifying the plan and org
  ownership requirement for repository-level settings
- An explicit plan requirement statement in the concepts page under
  'Who can configure content exclusion'

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: samueltauil

content/copilot/concepts/context/content-exclusion.md

@@ -26,6 +26,8 @@ You can use content exclusion to configure {% data variables.product.prodname_co
 
 Repository administrators, organization owners, and enterprise owners can configure content exclusion.
 
+Content exclusion requires a {% data variables.copilot.copilot_business_short %} or {% data variables.copilot.copilot_enterprise_short %} plan. This feature is not available for {% data variables.product.prodname_copilot_short %} plans assigned to personal accounts (such as {% data variables.copilot.copilot_free_short %}, {% data variables.copilot.copilot_pro_short %}, or {% data variables.copilot.copilot_pro_plus_short %}). Repositories must belong to an organization with an eligible plan for the content exclusion settings to appear.
+
 {% data reusables.copilot.content-exclusions-scope %}
 
 ### Availability of content exclusion

content/copilot/how-tos/configure-content-exclusion/exclude-content-from-copilot.md

@@ -30,6 +30,9 @@ category:
 
 You can use your repository settings to specify content in your repository that {% data variables.product.prodname_copilot %} should ignore.
 
+> [!NOTE]
+> Content exclusion settings are only available for repositories owned by an organization with a {% data variables.copilot.copilot_business_short %} or {% data variables.copilot.copilot_enterprise_short %} plan. If your repository is owned by a personal account, the **{% data variables.product.prodname_copilot_short %}** option will not appear in your repository settings. To configure content exclusion, the repository must belong to an organization that has a {% data variables.copilot.copilot_business_short %} or {% data variables.copilot.copilot_enterprise_short %} subscription.
+
 > [!NOTE]
 > {% data variables.copilot.copilot_cli %}, {% data variables.copilot.copilot_cloud_agent %}, and Agent mode in {% data variables.copilot.copilot_chat_short %} in IDEs, do not support content exclusion. For more information about these {% data variables.product.prodname_copilot_short %} features, see [AUTOTITLE](/copilot/concepts/agents/about-copilot-cli), [AUTOTITLE](/copilot/concepts/agents/cloud-agent/about-cloud-agent), and [AUTOTITLE](/copilot/how-tos/chat-with-copilot/chat-in-ide).