Use vitest globals (#27102) (#27311)

Backport #27102 by @silverwind

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

Co-authored-by: silverwind <me@silverwind.io>

web_src/js/utils/color.test.js

@@ -1,4 +1,3 @@
-import {test, expect} from 'vitest';
 import {useLightTextOnBackground} from './color.js';
 
 test('useLightTextOnBackground', () => {

web_src/js/utils/match.test.js

@@ -1,4 +1,3 @@
-import {test, expect} from 'vitest';
 import {matchEmoji, matchMention} from './match.js';
 
 test('matchEmoji', () => {

web_src/js/utils/url.test.js

@@ -1,4 +1,3 @@
-import {expect, test} from 'vitest';
 import {pathEscapeSegments} from './url.js';
 
 test('pathEscapeSegments', () => {