chore(auth): Remove skipConfirmationForEmailAddresses config

[nshirley]

Because:

• We added the new skipConfirmationForEmailRegex
• And we don't want multiple ways to manage skipping sign in confirmation emails

This Commit:

• Removes the older config
• Removes associated tests

Closes: FXA-13360

Sister PR: https://github.com/mozilla/webservices-infra/pull/10413 (this is just for stage so we can test with other teams that the regex is correct)

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• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).
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• Key files/areas to focus on:
  • The majority of changes to account.spec.ts is from formatting
  • I also added a test to make sure we're incrementing statsd when the bypass happens
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[Copilot]

Pull request overview

This PR removes the legacy signinConfirmation.skipForEmailAddresses configuration path in favor of the newer skipForEmailRegex, simplifying how sign-in confirmation bypass rules are configured.

Changes:

• Removed skipConfirmationForEmailAddresses handling from the account login bypass logic.
• Updated config schema/docs to drop skipForEmailAddresses and clarify skipForEmailRegex.
• Removed the email-address-list-based tests and added a StatsD assertion for the regex-based bypass path.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/fxa-auth-server/lib/routes/account.ts	Removes legacy email-list bypass logic; keeps regex-based bypass only.
packages/fxa-auth-server/lib/routes/account.spec.ts	Deletes old email-list tests; adds a StatsD assertion for emailAlways bypass; includes formatting churn.
packages/fxa-auth-server/config/index.ts	Removes deprecated config schema entry and updates skipForEmailRegex documentation.

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