service worker: Remove some LayoutTests that are redundant with WPT tests.

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/fetch-request-no-freshness-headers-worker.js

-var requests = [];
-
-self.addEventListener('message', function(event) {
-    event.data.port.postMessage({requests: requests});
-  });
-
-self.addEventListener('fetch', function(event) {
-    var url = event.request.url;
-    var headers = [];
-    for (var header of event.request.headers) {
-      headers.push(header);
-    }
-    requests.push({
-        url: url,
-        headers: headers
-      });
-    event.respondWith(fetch(event.request));
-  });