Changes

The Python decoder's decode_array() was not passing unshared=True when decoding array items, unlike decode_map() which correctly does this. This allowed nested shareable tags (tag 28) inside arrays to overwrite _share_index, causing subsequent shared references (tag 29) to resolve to the wrong object.

# [Tag 28 -> [Tag 28 -> 'a', 'b'], Tag 29 -> 0]
data = bytes.fromhex('82d81c82d81c61616162d81d00')
loads(data)
# Before: [['a', 'b'], 'b']  - shared ref returns 'b' instead of the array
# After:  [['a', 'b'], ['a', 'b']] - both elements are the same list object

The C decoder already handles this correctly.

Checklist

If this is a user-facing code change, like a bugfix or a new feature, please ensure that
you've fulfilled the following conditions (where applicable):

• You've added tests (in tests/) which would fail without your patch
• You've updated the documentation (in docs/), in case of behavior changes or new
  features
• You've added a new changelog entry (in docs/versionhistory.rst).

Updating the changelog

If there are no entries after the last release, use **UNRELEASED** as the version.
If, say, your patch fixes issue #123, the entry should look like this:

- Fix big bad boo-boo in the encoder
  (`#123 <https://github.com/agronholm/cbor2/issues/123>`_; PR by @yourgithubaccount)

If there's no issue linked, just link to your pull request instead by updating the
changelog after you've created the PR.