docs: Update method name for exchanging authorization code

According to DocBlock, the `authenticate` function is deprecated, meaning its use is no longer recommended.

Even though it may still work, I would recommend keeping the documentation as up to date as possible to prevent compatibility issues.

Author: akama-aka

docs/oauth-web.md

@@ -258,10 +258,10 @@ After completing the OAuth 2.0 flow, you should be redirected to `http://localho
 
 After the web server receives the authorization code, it can exchange the authorization code for an access token.
 
-To exchange an authorization code for an access token, use the `authenticate` method:
+To exchange an authorization code for an access token, use the `fetchAccessTokenWithAuthCode` method:
 
 ```php
-$client->authenticate($_GET['code']);
+$client->fetchAccessTokenWithAuthCode($_GET['code']);
 ```
 
 You can retrieve the access token with the `getAccessToken` method:
@@ -361,7 +361,7 @@ if (! isset($_GET['code'])) {
   $auth_url = $client->createAuthUrl();
   header('Location: ' . filter_var($auth_url, FILTER_SANITIZE_URL));
 } else {
-  $client->authenticate($_GET['code']);
+  $client->fetchAccessTokenWithAuthCode($_GET['code']);
   $_SESSION['access_token'] = $client->getAccessToken();
   $redirect_uri = 'http://' . $_SERVER['HTTP_HOST'] . '/';
   header('Location: ' . filter_var($redirect_uri, FILTER_SANITIZE_URL));