--multiple-versions option of bootstrap should disable constraints automatically.

[rd4398]

In e2e test for multiple version bootstrap flag we have

'tomli>=2.0,<=2.0.2' || true

The reason we need the || true here is that it tries to generate a constraints file, but that will never work when --multiple-versions is enabled.
We should make --multiple-versions disable constraints automatically.

Refer comment from @dhellmann here: #1035 (comment)