Fix multiple auth headers bug (#7703)

Fix https://github.com/FreshRSS/FreshRSS/issues/7699

lib/lib_rss.php

@@ -856,7 +856,7 @@ function checkTrustedIP(): bool {
 }
 
 function httpAuthUser(bool $onlyTrusted = true): string {
-	$auths = array_intersect_key($_SERVER, ['REMOTE_USER' => '', 'REDIRECT_REMOTE_USER' => '', 'HTTP_REMOTE_USER' => '', 'HTTP_X_WEBAUTH_USER' => '']);
+	$auths = array_unique(array_intersect_key($_SERVER, ['REMOTE_USER' => '', 'REDIRECT_REMOTE_USER' => '', 'HTTP_REMOTE_USER' => '', 'HTTP_X_WEBAUTH_USER' => '']));
 	if (count($auths) > 1) {
 		Minz_Log::warning('Multiple HTTP authentication headers!');
 		return '';