Fix dataframe CSV tests on Windows

[Guflly]

Fixes #20642.

The dataframe CSV sink wrapped a binary stream with default newline translation, which turned pandas CRLF endings into extra blank lines on Windows. Windowed test filenames also used colon-containing timestamps.

This disables newline translation for text sinks and uses the existing Windows-safe naming pattern in the windowed test, allowing the full IO test class to run on Windows.

Tests:

• python -m pytest -q apache_beam\dataframe\io_test.py (33 passed, 5 skipped)
• python -m yapf --diff apache_beam\dataframe\io.py apache_beam\dataframe\io_test.py

[gemini-code-assist]

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[github-actions]

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R: @jrmccluskey for label python.

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