Core: Remove pointless module.hot.decline() in addons

[tmeasday]

Closes #21340

What I did

Removed invalid ESM code from our addons. module is not defined in .mjs files, but tsup was passing this code through.

We were getting away with it because our WP rules were fairly permissive (not sure how it was working in Vite). Users seemed to trigger the issue by throwing away some of our rules, in combination with a move towards favouring .mjs more in #21161

The thing is, it didn't do anything anyway outside of developing the addon, AFAICT. @winkerVSbecks I'm not sure if we should keep it in addon-kit or not:

https://github.com/storybookjs/addon-kit/blob/4c3224fbbe9d3c663e88d11f563c91ebc10b0b4f/src/index.ts#L1-L3

How to test

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]