Use querySelector over alternative DOM methods (#31280)

As per
https://github.com/go-gitea/gitea/pull/30115#discussion_r1626060164,
prefer `querySelector` by enabling
[`unicorn/prefer-query-selector`](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/prefer-query-selector.md)
and autofixing all except 10 issues.

According to
[this](https://old.reddit.com/r/learnjavascript/comments/i0f5o8/performance_of_getelementbyid_vs_queryselector/),
querySelector may be faster as well, so it's a win-win.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

web_src/js/features/repo-diff.js

@@ -13,7 +13,7 @@ import {POST, GET} from '../modules/fetch.js';
 const {pageData, i18n} = window.config;
 
 function initRepoDiffReviewButton() {
-  const reviewBox = document.getElementById('review-box');
+  const reviewBox = document.querySelector('#review-box');
   if (!reviewBox) return;
 
   const counter = reviewBox.querySelector('.review-comments-counter');