Switch to have_current_path for MFA path comparison

[aduth]

🛠 Summary of changes

Updates flakey specs to use expect(page).to have_current_path … instead of expect(current_path).to eq ….

These tests have been shown to be occasionally flakey.

Examples:

• https://gitlab.login.gov/lg/identity-idp/-/jobs/1068613
• https://gitlab.login.gov/lg/identity-idp/-/jobs/1057968

Related Slack discussion: https://gsa-tts.slack.com/archives/C01710KMYUB/p1709311154032829

The hypothesis is there's a race condition where the test signs in with a new user and assumes to arrive at the MFA setup screen. This does happen, but only after a series of redirects, where the sign_in_before_mfa helper attempts to visit the account page.

The thought with using have_current_path is that it may help avoid some issues where the previous assertion would be made before the redirect is fully completed. While we don't allow any default wait, Capybara internally uses its document.synchronize logic which may still help "against asynchronicity problems" even if there is no measurable wait delay.

📜 Testing Plan

rspec spec/features/two_factor_authentication/multiple_mfa_sign_up_spec.rb

[aduth]

Follow-up: It appears this did not help, as there's still failures from these specs after this change.

Example: https://gitlab.login.gov/lg/identity-idp/-/jobs/1069991