[Bug]: `shopify theme dev` doesn't work with multipass passwords

[karreiro]

The shopify theme dev command doesn't work with multipass passwords, but it was working in the previous version.

Expected behavior

When users navigate to http://127.0.0.1:9292/account/login/multipass/<token>, it should log in (as it works with --legacy).

Actual behavior

When users navigate to http://127.0.0.1:9292/account/login/multipass/<token>, it presents an error.

Reproduction steps

1. Generate your multipass token
2. Open http://127.0.0.1:9292/account/login/multipass/<token>
3. Notice it doesn't work (but it works with the --legacy flag)