Removes vaOnlineSchedulingStatusImprovement feature flag from past ap…

[ryanshaw]

Note: This is part of a series of smaller PRs that breaks up the original large PR into more logical and reviewable chunks.

Summary

This removes the use of the va_online_scheduling_status_improvement feature flag from the src/applications/vaos/appointment-list/components/PastAppointmentsList/PastAppointmentsDateDropdown.jsx component within VA online scheduling. It is part of a set of PR's to address department-of-veterans-affairs/va.gov-team#55085. We no longer use this feature flag, so code behind this flag can be removed.

Related issue(s)

department-of-veterans-affairs/va.gov-team#55085

Testing done

• Unit testing
• e2e testing
• Manual local testing

Acceptance criteria

Quality Assurance & Testing

• I updated 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

Error Handling

• Browser console contains no warnings or errors.
• Events are being sent to the appropriate logging solution

Authentication

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

[jenniemc]

LGTM!