Fix 405 response of NCN version lister

lib/REST/NextCloudNews/Versions.php

@@ -11,7 +11,7 @@ class Versions implements \JKingWeb\Arsse\REST\Handler {
     public function dispatch(\JKingWeb\Arsse\REST\Request $req): Response {
         // if a method other than GET was used, this is an error
         if ($req->method != "GET") {
-            return new Response(405);
+            return new Response(405, "", "", ["Allow: GET"]);
         }
         if (preg_match("<^/?$>", $req->path)) {
             // if the request path is an empty string or just a slash, return the supported versions

tests/REST/NextCloudNews/TestNCNVersionDiscovery.php

@@ -26,7 +26,7 @@ class TestNCNVersionDiscovery extends Test\AbstractTest {
     }
 
     public function testUseIncorrectMethod() {
-        $exp = new Response(405);
+        $exp = new Response(405, "", "", ["Allow: GET"]);
         $h = new REST\NextCloudNews\Versions();
         $req = new Request("POST", "/");
         $res = $h->dispatch($req);