Fix heading elements on 686c-674 and 28-1900 introduction pages

[zack]

department-of-veterans-affairs/va.gov-team#64130

Summary

• Some headers were using the wrong headings in the form introduction pages, breaking accessibility guidelines.
• This fix changes some <h4>s to <h3>s to bring us back into compliance.

Related issue(s)

• [a11y-defect-2]: Incorrect heading levels on process list component va.gov-team#64130

Testing done

• Checked the new headers using HeadingsMap

Screenshots

Note: This field is mandatory for UI changes (non-component work should NOT have screenshots).

	Before	After
686c-674
28-1900

What areas of the site does it impact?

Just these two forms

Acceptance criteria

Quality Assurance & Testing

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Linting warnings have been addressed
• Documentation has been updated (link to documentation *if necessary)
• Screenshot of the developed feature is added
• Accessibility testing has been performed

Error Handling

• Browser console contains no warnings or errors.
• Events are being sent to the appropriate logging solution
• Feature/bug has a monitor built into Datadog or Grafana (if applicable)

Authentication

• Did you login to a local build and verify all authenticated routes work as expected with a test user

⚠️ Team Sites (only applies to modifications made to the VA.gov header) ⚠️

• The vets-website header does not contain any web-components
• I used the proxy-rewrite steps to test the injected header scenario
• I reached out in the #sitewide-public-websites Slack channel for questions

Requested Feedback

(OPTIONAL) What should the reviewers know in addition to the above. Is there anything specific you wish the reviewer to assist with. Do you have any concerns with this PR, why?

[Midge-dev]

LGTM 🤙

[zack]

@department-of-veterans-affairs/benefits-team-1-frontend
@department-of-veterans-affairs/vsa-authd-exp-frontend
@department-of-veterans-affairs/dbex-trex

Is anyone available to give this a review? Thanks :)

[Mottie]

Awesome!