revert: remove oauth2.php fix (moved to standalone PR Cacti#6886)

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

Author: somethingwithproof

oauth2.php

@@ -92,9 +92,7 @@
 if (!isrv('code')) { // If we don't have an authorization code then get one
 	$authUrl                 = $provider->getAuthorizationUrl($options);
 	$_SESSION['oauth2state'] = $provider->getState();
-	header('Location: ' . $authUrl);
-
-	exit;
+	cacti_redirect($authUrl, false);
 
 	// Check given state against previously stored one to mitigate CSRF attack
 }