docs: replace the MinIO recommendation in the object storage section

[Iheanacho-ai]

What

Rewrites the Object storage section of kubernetes-guides/csi/storage.mdx to
drop the MinIO recommendation.

Why

Closes #764. The section called MinIO "one of the most popular open source add-on
object stores". The minio/minio repository is archived (GitHub API:
archived: true, last push 2026-04-24), so the page recommended a project that no
longer takes changes.

Change

• Remove the MinIO recommendation, with no replacement caveat about its status,
  licence or archive date — dated vendor claims rot, and the reported archive
  dates disagree.
• Note that object stores are common, and name Rook/Ceph and SeaweedFS as two
  examples already covered on this page, linked to their upstream object storage
  documentation.

Testing

• Ran: make broken-links, make validate-docs-nav,
  make style-check-changed STYLE_CHECK_BASE=upstream/main, make docs.json.
  All pass; style 0 errors / 0 warnings; no docs.json drift.
• Where: local checkout, containerised targets.
• By: Claude Opus 5, reviewed by me.
• Filled from outside the page: the section is prose only and documents no
  commands, so there is nothing to run.

[github-actions]

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