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/repo-unicode-escape.js

@@ -1,3 +1,5 @@
+import $ from 'jquery';
+
 export function initUnicodeEscapeButton() {
   $(document).on('click', 'a.escape-button', (e) => {
     e.preventDefault();