Rename Toolkit's webextensions component directory to better reflect what it is.

toolkit/components/extensions/test/mochitest/webrequest_test.jsm

@@ -1,22 +0,0 @@
-"use strict";
-
-this.EXPORTED_SYMBOLS = ["webrequest_test"];
-
-Components.utils.importGlobalProperties(["fetch", "XMLHttpRequest"]);
-
-this.webrequest_test = {
-  testFetch(url) {
-    return fetch(url);
-  },
-
-  testXHR(url) {
-    return new Promise(resolve => {
-      let xhr = new XMLHttpRequest();
-      xhr.open("HEAD", url);
-      xhr.onload = () => {
-        resolve();
-      };
-      xhr.send();
-    });
-  },
-};