fix mention of amplify add auth in gen2 auth (#6538)

Co-authored-by: Nikhil Swaminathan <2429410+swaminator@users.noreply.github.com>

src/pages/gen2/build-a-backend/auth/add-social-provider/index.mdx

@@ -23,7 +23,7 @@ The preferred way to incorporate social provider sign-in is via an OAuth redirec
 
 [OAuth 2.0](https://en.wikipedia.org/wiki/OAuth) is the common Authorization framework used by web and mobile applications for accessing user information ("scopes") in a limited manner. Common analogies you will hear in OAuth is that of boarding a plane or staying in a hotel - showing your identification is the authentication piece (signing into an app) and using the boarding pass/hotel key is what you are authorized to access.
 
-OAuth support in Amplify uses Cognito User Pools and supports federation with social providers, which will automatically create a corresponding user in the User Pool after they sign in. With this design you do not need to include an SDK for the social provider in your app. After you set up your developer account with these social providers you can configure the `Auth` category by running `amplify add auth` and selecting the social provider option. You can then use `signInWithRedirect()` in your app to either show a pre-built "Hosted UI" or pass in a provider name (e.g. `signInWithRedirect({ provider: 'Facebook' })`) to interface directly and build your own UI. ![Image](/images/SocialAuthZ.png)
+OAuth support in Amplify uses Cognito User Pools and supports federation with social providers, which will automatically create a corresponding user in the User Pool after they sign in. With this design you do not need to include an SDK for the social provider in your app. After you set up your developer account with these social providers you can configure by specifying `externalProviders` under `loginWith`. You can then use `signInWithRedirect()` in your app to either show a pre-built "Hosted UI" or pass in a provider name (e.g. `signInWithRedirect({ provider: 'Facebook' })`) to interface directly and build your own UI. ![Image](/images/SocialAuthZ.png)
 
 </Accordion>