Remove migration-signup flow

[daledupreez]

Details

We have limited traffic that is currently flowing to the /setup/migration-signup flow, with most of those users being redirected from the entrepreneur flow.

Once we deployed #100938 to direct users from the entrepreneur flow to the site-migration flow instead, we should be a in a position to remove this flow.

We may need a redirect to /setup/hosted-site-migration or /setup/migration to catch any lingering traffic, but we can determine that a week or so after we fix the redirect.

Checklist

• Determine current flow volume at least a week after deploying Redirect entrepreneur flow to site-migration flow #100938
• Determine whether we need a redirect -- if so, add a redirect
• Remove the flow

Related

No response