Bump fsspec from 2024.12.0 to 2025.3.1 in /backend

Bumps [fsspec](https://github.com/fsspec/filesystem_spec) from 2024.12.0 to 2025.3.1.
- [Commits](fsspec/filesystem_spec@2024.12.0...2025.3.1)

---
updated-dependencies:
- dependency-name: fsspec
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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Author: dependabot[bot]