Fix Copilot Pro+ signup attribution

Author: sbaidon

content/copilot/how-tos/set-up/set-up-for-self.md

@@ -23,7 +23,7 @@ There are a few ways that you can get access to {% data variables.product.prodna
 * **Sign up for a paid plan**. You can subscribe to one of these plans:
 
   * **{% data variables.copilot.copilot_pro_short %}**, which includes access to premium models and a monthly allowance of {% data variables.product.prodname_ai_credits_short %}. [Subscribe to {% data variables.copilot.copilot_pro_short %}](https://github.com/github-copilot/signup?ref_product=copilot&ref_type=purchase&ref_style=text&ref_plan=pro).
-  * **{% data variables.copilot.copilot_pro_plus_short %}**, which includes a higher monthly allowance of {% data variables.product.prodname_ai_credits_short %} and access to all available models. [Subscribe to {% data variables.copilot.copilot_pro_plus_short %}](https://github.com/github-copilot/signup?ref_product=copilot&ref_type=purchase&ref_style=text&ref_plan=pro).
+  * **{% data variables.copilot.copilot_pro_plus_short %}**, which includes a higher monthly allowance of {% data variables.product.prodname_ai_credits_short %} and access to all available models. [Subscribe to {% data variables.copilot.copilot_pro_plus_short %}](https://github.com/github-copilot/signup?ref_product=copilot&ref_type=purchase&ref_style=text&ref_plan=pro-plus).
   * **{% data variables.copilot.copilot_max_short %}**, which includes advanced AI models and our highest individual monthly allowance of {% data variables.product.prodname_ai_credits_short %}. [Subscribe to {% data variables.copilot.copilot_max_short %}](https://github.com/settings/billing/licensing?ref_product=copilot&ref_type=purchase&ref_style=text&ref_plan=max).
 
 * **Use {% data variables.product.prodname_copilot_short %} through your organization or enterprise**. If you're part of an organization or enterprise with a {% data variables.product.prodname_copilot_short %} plan, you can request access at [https://github.com/settings/copilot](https://github.com/settings/copilot) under "Get {% data variables.product.prodname_copilot_short %} from an organization."