Fix Apache Beam hook type error with mypy 2.2.0 typeshed

[FrankYang0529]

Why

• The daily CI environment upgrade (#69694) bumps mypy 2.1.0 → 2.2.0, and MyPy providers checks fails on it.

    providers/apache/beam/src/airflow/providers/apache/beam/hooks/beam.py:184: error: Value of type variable "_R" of "select" cannot be "IO[Any] | None"  [type-var]
                readable_fds, _, _ = select.select(reads, [], [], 5)
                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Found 1 error in 1 file (checked 4688 source files)

How

• Filter out None before passing the descriptors to select.select.

Verification

breeze run --python 3.10 --backend none --tty disabled bash -c "
  uv pip install --system -q mypy==2.2.0
  cd /opt/airflow
  mypy providers/apache/beam/src/airflow/providers/apache/beam/hooks/beam.py
"

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• Yes (please specify the tool below)

---

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