Drop attrs typing workaround

[AdrianSosic]

Now fixed upstream in the new attrs version.

• Make validators optional in deep_mapping python-attrs/attrs#1448
• Allow deep_iterable and deep_mapping take lists/tuples python-attrs/attrs#1449

[AdrianSosic]

Blocker to wait until the next attrs version is out

[AVHopp]

Approving since this is already blocked by @Scienfitz review

[Copilot]

Pull Request Overview

This PR removes attrs typing workarounds that were previously needed due to upstream issues in the attrs library, now that these issues have been fixed in the new attrs version.

• Updates the attrs dependency requirement from >=24.1.0 to >=25.4.0
• Removes workaround lambda functions and imports that were needed for older attrs versions
• Simplifies validator syntax to use the now-supported list format

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
pyproject.toml	Updates attrs dependency to version 25.4.0 to enable removal of workarounds
baybe/utils/metadata.py	Removes lambda workaround for value_validator in deep_mapping
baybe/parameters/substance.py	Removes and_ import and replaces validator syntax with list format

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