fix: end the browser speed test feed without a 410 or 502

internal/server/web/templates/status.html

@@ -167,7 +167,7 @@
       for (var i = 0; i < n; i++) parts.push(block);
       return fetch(base + '/speed/down', {method: 'POST', body: new Blob(parts), credentials: 'same-origin', signal: stop.signal})
         .then(function (r) {
-          if (!r.ok) return;
+          if (r.status !== 204) return;
           if (performance.now() - t < 500 && n < 256) n *= 2;
           return one();
         });