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

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[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.16%. Comparing base (9c561e2) to head (00b4954).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #39563   +/-   ##
=========================================
  Coverage     58.16%   58.16%           
  Complexity    13086    13086           
=========================================
  Files          2521     2521           
  Lines        264569   264569           
  Branches      10788    10788           
=========================================
+ Hits         153879   153882    +3     
+ Misses       104923   104920    -3     
  Partials       5767     5767           

Flag	Coverage Δ
python	79.83% <ø> (+<0.01%)	⬆️

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