Fix accessibility: Add row headers to premium features table (#60150)

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

Author: heiskr

content/copilot/concepts/billing/copilot-requests.md

@@ -35,6 +35,8 @@ Some {% data variables.product.prodname_copilot_short %} features use more advan
 
 The following {% data variables.product.prodname_copilot_short %} features can use premium requests.
 
+{% rowheaders %}
+
 | Feature | Premium request consumption | SKU Attribution |
 | ------- | ----------- | ----------- |
 | [{% data variables.copilot.copilot_chat_short %}](/copilot/using-github-copilot/copilot-chat) | {% data variables.copilot.copilot_chat_short %} uses **one premium request** per user prompt, multiplied by the model's rate. This includes ask, edit, agent, and plan modes in {% data variables.copilot.copilot_chat_short %} in an IDE. | {% data variables.product.prodname_copilot_short %} premium requests |
@@ -46,6 +48,8 @@ The following {% data variables.product.prodname_copilot_short %} features can u
 | [{% data variables.product.prodname_openai_codex %} {% data variables.product.prodname_vscode %} integration](/copilot/concepts/agents/openai-codex) | While in preview, each prompt to {% data variables.product.prodname_openai_codex %} uses **one premium request** multiplied by the model multiplier rates. | {% data variables.product.prodname_copilot_short %} premium requests |
 | [Third-party coding agents](/free-pro-team@latest/copilot/concepts/agents/about-third-party-agents) | While in preview, each prompt to a third-party coding agent uses **one premium request**. | {% data variables.product.prodname_copilot_short %} premium requests |
 
+{% endrowheaders %}
+
 
 > [!TIP]
 > For instructions on viewing how many premium requests you have used and advice on how to optimize usage, see [AUTOTITLE](/copilot/how-tos/manage-and-track-spending/monitor-premium-requests).