Remove duplicate "Open Email App" in Onboarding

[vknabel]

PR Creator Checklist

As this is just a small and obvious text-fix, I did not clone this repo and discussed the changes before opening this PR. And as testing this, would require me to create a new Account, I did not test it either.

Summary

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Removed the duplicate Open Email App on the onboarding. It seems to be a leftover.

Screenshots

If the UI has been changed, include screenshots. We will not review your PR without screenshots if they are applicable.

Making a screenshot would require lots of unnecessary work on my side, due to the simplicity of this change.

Test Plan

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Create an Account and have a look on the onboarding.openEmailAppBtn.