Fix incorrect handler location for list of branches

What does this MR do and why?

Contributes to #408438 (closed)

Problem

Nothing happens when user clicks on the branch name on commit page. In the JS console appears TypeError: this.querySelector(...) is null.

We use an uncorrect selector for branches expand action. Instead of adding a handle for a special expand button, we use the whole branches block.

Solution

Change handler from .commit-info (block with branches) to .js-details-expand (expand button).

How to set up and validate locally

1. Open http://127.0.0.1:3000/root/gitlab-test/-/commit/ddd0f15ae83993f5cb66a927a28673882e99100b
2. Click on ...
3. You should see all related branches
4. Click on master
5. You should be redirected to master branch page

MR acceptance checklist

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