The acceptance test added in c5a6754e29 ("voting on a post and removing
vote updates the count reactively") was written against the pre-BEM
class names and has been failing on `main` ever since.
PR #39443 (8e44060201) renamed the post-voting button and vote-count
classes to BEM form — `.post-voting-post-toggle-voters` →
`.post-voting-post__toggle-voters`, `.post-voting-button-upvote` →
`.post-voting-button.--upvote`, `.post-voting-button-voted` → `--voted`,
etc. It landed before #39416, but #39416 rebased over it without
updating the new test's selectors, so the assertions look for elements
that no longer exist and every frontend CI run now fails with "Element
#post_2 .post-voting-post-toggle-voters should exist".
Point the selectors at the current BEM names. The sibling tests in the
same file (e.g. the comment-voting test just above) already use this
form, so this only brings the new test in line with the rest.
1e07278750
