feat(deps): update @rspack/core to 1.4.0-rc.0

[chenjiahan]

Summary

Update @rspack/core to 1.4.0-rc.0 and fix test cases.

Related Links

https://github.com/web-infra-dev/rspack/releases/tag/v1.4.0-rc.0

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR updates the @rspack/core dependency to the 1.4.0-rc.0 release candidate and adjusts an existing end-to-end test to match the updated configuration validation error message.

• Bump @rspack/core version from 1.4.0-beta.1 to 1.4.0-rc.0
• Update expected error message in rspack-config-validate e2e test

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/core/package.json	Upgrade @rspack/core dependency to 1.4.0-rc.0
e2e/cases/config/rspack-config-validate/index.test.ts	Update test assertion to match new error message format

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported