THEMES-967: Node 16 | Remove enzyme tests from ad block

[vgalatro]

Description

This PR converts tests using enzyme to use @testing-library/react instead.

Jira Ticket

• THEMES-967

Acceptance Criteria

Convert test to use @testing-library/react

Test Steps

1. Checkout this branch git checkout THEMES-967
2. Run npm run test:coverage
3. The tests should pass for the ads-block and the coverage should be acceptable.

Author Checklist

• Confirmed all the test steps a reviewer will follow above are working.
• Confirmed there are no linter errors. Please run npm run lint to check for errors. Often, npm run lint:fix will fix those errors and warnings.
• Ran this code locally and checked that there are not any unintended side effects. For example, that a CSS selector is scoped only to a particular block.
• Confirmed this PR has reasonable code coverage. You can run npm run test:coverage to see your progress.
  • Confirmed this PR has unit test files
  • Ran npm run test, made sure all tests are passing
  • If the amount of work to write unit tests for this change are excessive,
    please explain why (so that we can fix it whenever it gets refactored).
• Confirmed relevant documentation has been updated/added.

Reviewer Checklist

The reviewer of the PR should copy-paste this template into the review comments on review.

• Linting code actions have passed.
• Ran the code locally based on the test instructions.
  • I don’t think this is needed to be tested locally. For example, a padding style change (storybook?) or a logic change (write a test).
• I am a member of the engine theme team so that I can approve and merge this. If you're not on the team, you won't have access to approve and merge this pr.
• Looked to see that the new or changed code has code coverage, specifically. We want the global code coverage to keep on going up with targeted testing.

[blakeganderson]

LGTM! All tests passed