Use explicit jQuery import, remove unused eslint globals (#18435)

- Don't rely on globals (window.$) for jQuery import
- Remove eslint globals no longer in use

web_src/js/features/user-auth-webauthn.js

@@ -1,8 +1,8 @@
+import $ from 'jquery';
 import {encode, decode} from 'uint8-to-base64';
 
 const {appSubUrl, csrfToken} = window.config;
 
-
 export function initUserAuthWebAuthn() {
   if ($('.user.signin.webauthn-prompt').length === 0) {
     return;