CHK-3367: fix shipping line fee

[bold-nima]

Jira Issue

Description

This fixes the issue where when we change the shipping method the amount doesn't get updated. We want to use code instead of index.

Testing

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce the testing. Also, list any relevant details for your test configuration.

Checklist

• I have tested this change myself
• I have created specs/tests for these changes (if applicable)
• I have updated the documentation (if applicable)
• I have bumped the version by more than 1 - ex. 1.0.1-build.344 becomes 1.0.1-build.346

Repo Resources

Below are two shops with META that can be used for QA-ing

Internal Production Store

Internal Staging Store

[swarmia]

✅  Linked to Bug CHK-3367 · Order total is incorrect after returning to shipping method page
➡️  Part of Epic CHK-1373 · Ensure SimpleOrder is supported in Adobe Commerce