Use vitest globals (#27102)

Enable [globals](https://vitest.dev/config/#globals) in vitest, reducing
the noise in test files.

web_src/js/modules/fetch.test.js

@@ -1,4 +1,3 @@
-import {test, expect} from 'vitest';
 import {GET, POST, PATCH, PUT, DELETE} from './fetch.js';
 
 // tests here are only to satisfy the linter for unused functions

web_src/js/modules/toast.test.js

@@ -1,4 +1,3 @@
-import {test, expect} from 'vitest';
 import {showInfoToast, showErrorToast, showWarningToast} from './toast.js';
 
 test('showInfoToast', async () => {