Fix: wrong redirect after how to migrate step

[andres-blanco]

Related to #94126

Proposed Changes

Redirect to the credential collection step after a user with a plan selects the DIFM option on the HOW_TO_MIGRATE step.

Why are these changes being made?

This fixes a bug on the site-migration flow. If a user with a plan selected the option DIFM on the HOW_TO_MIGRATE step they got redirected to the /migrateMessage step. This is wrong, since we should be sending users to the credential collection step.

More context: p1725373567345639/1725364409.566409-slack-C0Q664T29

Testing Instructions

1. Apply this diff or navigate to the calypso.live link below
2. Navigate to /start
3. Select a Business plan
4. Select import as intent
5. Go through the flow and select Do it for me on the How to migrate step
6. Verify you are redirected to the credential collection step

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-118178

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-118178&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-118178&env=a8c-for-agencies

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~25 bytes added 📈 [gzipped])

name                        parsed_size           gzip_size
site-migration-flow              +146 B  (+0.2%)      +13 B  (+0.1%)
hosted-site-migration-flow       +146 B  (+0.2%)      +12 B  (+0.1%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[markbiek]

LGTM!

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• notifications

To test WordPress.com changes, run install-plugin.sh $pluginSlug fix/wrong-redirect-after-howto-step on your sandbox.