feat: bump axe core to 4.2.1 and fix unit test's failures

[lpelypenko]

Summary

• bumped axe core to 4.2.1
• updated snapshots

4.2.1 version has greatly improved vs 4.0.1 with major fixes and greater coverge.

I would like to start using it in our team but the old version 4.0. 1is showing false negative issues for 'button-name' and 'svg-img-alt' rules that were fixed in 4.2.1.

I would really appreciate it if this change gets merged.

[lpelypenko]

Hi @NickColley ,
I would really appreciate if you consider to merge this library update and bump jest-axe.
We keep seeing the issue from axe-core old version (august 2020 version) that is just an incorrect axe core rule that was fixed before. Example(removed some real names from classes):

    Expected the HTML found at $('.test-class') to have no violations:

    <svg xmlns="swgUrl" focusable="false" role="img" fill="currentColor" viewBox="0 0 24 24" class="test-class">

    Received:

    "svg elements with an img role have an alternative text (svg-img-alt)"

    Fix any of the following:
      Element child title is empty
      aria-label attribute does not exist or is empty
      aria-labelledby attribute does not exist, references elements that do not exist or references elements that are empty
      Element has no title attribute

When test-class svg has a title that fix such violation:

<svg xmlns="swgUrl" focusable="false" role="img" fill="currentColor" viewBox="0 0 24 24" class="test-class">
<title>Hide chart</title>
<path d="some correct path">
</path>
</svg>

This issue is not reproducible with axe-core 4.2.1 and the current MR would be really helpful for me to unblock usage of jest-axe.

Thank you in advance for your time!

[NickColley]

Running CI for this and will merge and publish as a breaking change if it succeeds. (Since new rules result in builds changing, small breaking change for some people)...