Bump immutable from 5.1.4 to 5.1.5 in /website (#5244)

Bumps [immutable](https://github.com/immutable-js/immutable-js) from 5.1.4 to 5.1.5.
- [Release notes](https://github.com/immutable-js/immutable-js/releases)
- [Changelog](https://github.com/immutable-js/immutable-js/blob/main/CHANGELOG.md)
- [Commits](https://github.com/immutable-js/immutable-js/compare/v5.1.4...v5.1.5)

---
updated-dependencies:
- dependency-name: immutable
  dependency-version: 5.1.5
  dependency-type: indirect
...

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