fix(modern-module): remove extra import statement for star reexport

[fi3ework]

Summary

Fix https://github.com/web-infra-dev/rslib/issues/429.

Previously given a module like this:

export * from "external1"

the diff of the output after this PR will be

- import * as __WEBPACK_EXTERNAL_MODULE_external1__ from "external1";
export * from "external1"

Checklist

• [x] Tests updated (or not required).
• [ ] Documentation updated (or not required).

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