Send confirmation instructions to provisioned by group users if needed

What does this MR do and why?

While working on enterprise_users_automatic_claim feature flag removal, I found a regression caused on Oct 20, 2023 after globally enabling this feature flag.

Before enterprise_users_automatic_claim rollout, every provisioned by a group user received an old enterprise user email notification with confirmation link. In Resolve "Provisoned Accounts - Welcome Email" (!51271 - merged) we disabled sending Confirmation instructions email with a confirmation link to all provisioned by group users to resolve Duplicate emails with confirmation links are se... (#341718 - closed).

After the rollout of enterprise_users_automatic_claim, we disabled sending the old enterprise user email notification and send new enterprise user email to enterprise users only. This means if a group hasn't verified their domains to adopt enterprise_users_automatic_claim and bypass email confirmation for provisioned users, then provisioned by that group users do not receive an email with a confirmation link to confirm their account. We should send Confirmation instructions email with a confirmation link to provisioned by group users to let them confirm their account in that case.

This MR enables sending Confirmation instructions email with a confirmation link to provisioned by group users if needed(1).

(1) If a group verified their domains to adopt enterprise_users_automatic_claim and bypass email confirmation for provisioned users, then provisioned by that group users would be automatically confirmed and they

• won't receive Confirmation instructions email with a confirmation link.
• will receive new enterprise user email but it will not include a confirmation link.

Since Confirmation instructions email with confirmation link will be sent to enterprise users unless they are automatically confirmed, this MR removes the confirmation link from the enterprise user email to resolve Duplicate emails with confirmation links are se... (#341718 - closed)

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