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/components/DiffFileTree.vue

@@ -112,7 +112,7 @@ export default {
     updateState(visible) {
       const btn = document.querySelector('.diff-toggle-file-tree-button');
       const [toShow, toHide] = btn.querySelectorAll('.icon');
-      const tree = document.getElementById('diff-file-tree');
+      const tree = document.querySelector('#diff-file-tree');
       const newTooltip = btn.getAttribute(visible ? 'data-hide-text' : 'data-show-text');
       btn.setAttribute('data-tooltip-content', newTooltip);
       toggleElem(tree, visible);