socket.io: Delete ignored `resource` option

I couldn't find any reference to a `resource` option in either the
socket.io-client documentation or its source code.

src/static/js/admin/plugins.js

@@ -7,11 +7,10 @@ $(document).ready(() => {
   const pathComponents = location.pathname.split('/');
   // Strip admin/plugins
   const baseURL = `${pathComponents.slice(0, pathComponents.length - 2).join('/')}/`;
-  const resource = `${baseURL.substring(1)}socket.io`;
 
   // connect
   const room = `${url}pluginfw/installer`;
-  const socket = io.connect(room, {path: `${baseURL}socket.io`, resource});
+  const socket = io.connect(room, {path: `${baseURL}socket.io`});
 
   const search = (searchTerm, limit) => {
     if (search.searchTerm !== searchTerm) {

src/static/js/admin/settings.js

@@ -7,11 +7,10 @@ $(document).ready(() => {
   const pathComponents = location.pathname.split('/');
   // Strip admin/plugins
   const baseURL = `${pathComponents.slice(0, pathComponents.length - 2).join('/')}/`;
-  const resource = `${baseURL.substring(1)}socket.io`;
 
   // connect
   const room = `${url}settings`;
-  const socket = io.connect(room, {path: `${baseURL}socket.io`, resource});
+  const socket = io.connect(room, {path: `${baseURL}socket.io`});
 
   socket.on('settings', (settings) => {
     /* Check whether the settings.json is authorized to be viewed */

src/static/js/pad.js

@@ -223,13 +223,10 @@ const handshake = () => {
   const port = loc.port === '' ? (loc.protocol === 'https:' ? 443 : 80) : loc.port;
   // create the url
   const url = `${loc.protocol}//${loc.hostname}:${port}/`;
-  // find out in which subfolder we are
-  const resource = `${exports.baseURL.substring(1)}socket.io`;
   // connect
   socket = pad.socket = io.connect(url, {
     // Allow deployers to host Etherpad on a non-root path
     path: `${exports.baseURL}socket.io`,
-    resource,
     reconnectionAttempts: 5,
     reconnection: true,
     reconnectionDelay: 1000,

src/static/js/timeslider.js

@@ -56,11 +56,9 @@ const init = () => {
     const port = loc.port === '' ? (loc.protocol === 'https:' ? 443 : 80) : loc.port;
     // create the url
     const url = `${loc.protocol}//${loc.hostname}:${port}/`;
-    // find out in which subfolder we are
-    const resource = `${exports.baseURL.substring(1)}socket.io`;
 
     // build up the socket io connection
-    socket = io.connect(url, {path: `${exports.baseURL}socket.io`, resource});
+    socket = io.connect(url, {path: `${exports.baseURL}socket.io`});
 
     // send the ready message once we're connected
     socket.on('connect', () => {