test: remove redundant import and streaming-stub smoke checks

[ttuff]

Motivation

• Remove overlapping, low-value smoke assertions to reduce test churn while keeping focused contract coverage intact.

Description

• Deleted a duplicate __version__ presence check from src/cubedynamics/tests/test_import_and_pipe.py and removed redundant streaming-stub NotImplementedError assertions from src/cubedynamics/tests/test_imports.py, keeping the explicit stub and download behavior tests in src/cubedynamics/tests/test_streaming_contracts.py.

Testing

• Ran pytest src/cubedynamics/tests/test_imports.py src/cubedynamics/tests/test_import_and_pipe.py src/cubedynamics/tests/test_streaming_contracts.py -q which passed (7 passed, 1 warning) and ran pytest --collect-only -q which reported 231 collected tests.

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Codex Task