fix(docs): fix link formatting in external identity providers doc (#8250)

Author: noid11

src/pages/[platform]/build-a-backend/auth/concepts/external-identity-providers/index.mdx

@@ -256,7 +256,7 @@ You need to now inform your external provider of the newly configured authentica
 </Block>
 </BlockSwitcher>
 
-Learn more about using social identity providers with user pool](https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-pools-social-idp.html)
+[Learn more about using social identity providers with user pool](https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-pools-social-idp.html)
 
 ### Customizing scopes for retrieving user data from external providers