Fixed type for Auth.federatedSignIn() in lib/auth/js/social (aws-amplify#4699)

Author: nadetastic

src/fragments/lib/auth/js/social.mdx

@@ -143,7 +143,7 @@ When using the federated OAuth flow with Cognito User Pools, the [device trackin
 
 ## Setup frontend
 
-After configuring the OAuth endpoints (Cognito Hosted UI), you can integrate your App by invoking `Auth.federatedSignIn()` function. Passing `LoginWithAmazon`, `Facebook`, `Google`, or `SignInWithApple` on the `provider` argument (e.g `Auth.federatedSign({ provider: 'LoginWithAmazon' })`), it will bypass the Hosted UI and federate immediately with the social provider as shown in the below React example. If you are looking to add a custom state, you are able to do so by passing a string (e.g. `Auth.federatedSignIn({ customState: 'xyz' })`) value and listening for the custom state via Hub.
+After configuring the OAuth endpoints (Cognito Hosted UI), you can integrate your App by invoking `Auth.federatedSignIn()` function. Passing `LoginWithAmazon`, `Facebook`, `Google`, or `SignInWithApple` on the `provider` argument (e.g `Auth.federatedSignIn({ provider: 'LoginWithAmazon' })`), it will bypass the Hosted UI and federate immediately with the social provider as shown in the below React example. If you are looking to add a custom state, you are able to do so by passing a string (e.g. `Auth.federatedSignIn({ customState: 'xyz' })`) value and listening for the custom state via Hub.
 
 ```javascript
 import React, { useEffect, useState } from 'react';