fix: always show email address for order summaries

[dkoo]

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Changes proposed in this Pull Request:

#1550 introduced a custom template to force the "order summary" to appear in the thank-you template when completing a transaction using an email address that's already registered on the site. However, this custom template inherited some logic which only exposed the order's email address if it matches the currently logged-in user. Since this template is only shown in scenarios where a non-logged-in user is completing a transaction using an existing account's email, that condition will never be satisfied, so this PR removes the logic and always shows the email address in the order summary. This should be safe because we're checking the order key before showing order summary details to ensure that the order details are only shown during the course of a checkout flow involving that exact order.

How to test the changes in this Pull Request:

1. Complete testing steps for fix: match thankyou template when using existing customer email #1550.
2. On release, observe that no email address is shown on the thank you screen.
3. On this branch, confirm that the email address is shown.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[matticbot]

🎉 This PR is included in version 1.75.5 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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