TOTPs not required for WebAuthn device

What does this MR do?

Previously, you had to use a time-based one-time password (TOTP) before you could add a WebAuthn device as a two-factor authentication (2FA) method on your GitLab account. From GitLab 15.9, you can add a WebAuthn device as your 2FA method without having to use a TOTP. You must download recovery codes when adding a WebAuthn device as your 2FA method so you can recover access to your account if you are locked out. This documentation changes reflects this. See gitlab-com/www-gitlab-com!117506 (merged) for the release post item MR.

This change also clarifies that:

• A WebAuthn device is bound to a particular web browser on a specific computer.
• When you set up a WebAuthn device, you enter a device name and password, and you might not need to enter this password if you have signed in through your identity provider.
• Clearing the browser data could lead to the user unable to sign-in and they would need to set up the device again.

Related issues

gitlab-org/manage/general-discussion#17597

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