Fix precommit python version bug

[heyufan1995]

No description provided.

[greptile-apps]

Greptile Summary

This PR fixes a pre-commit failure by removing a None | None expression (PEP 604 syntax requiring Python ≥ 3.10) from inside a Union[] annotation in typing.py, and updates both README environment setup instructions to match the py311 target already declared in pyproject.toml.

Confidence Score: 5/5

Safe to merge — targeted two-line fix with no logic changes and consistent documentation updates.

All three changes are correct and minimal: the None | None removal eliminates a genuine syntax incompatibility, and both README updates align docs with the existing py311 ruff target. No regressions introduced.

No files require special attention.

Important Files Changed

Filename	Overview
NV-Segment-CTMR/brain_t1_preprocess/intensity_normalization/typing.py	Removes redundant `None
NV-Segment-CTMR/docs/README.md	Updates conda environment creation from python=3.9 to python=3.11, aligning with the target-version = "py311" already set in pyproject.toml.
NV-Segment-CT/docs/README.md	Same Python version update (3.9 → 3.11) in the sister CT-module README, keeping both docs consistent.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["ArgType definition\n(before)"] --> B["Union[Namespace, list[str], None | None]"]
    B --> C{"Python version?"}
    C -->|"3.9 — NoneType has no __or__"| D["TypeError at module load"]
    C -->|"3.10+ — PEP 604 supported"| E["Resolves to Union[Namespace, list[str], None]\n(redundant but valid)"]

    F["ArgType definition\n(after)"] --> G["Union[Namespace, list[str], None]"]
    G --> H["Valid on all targeted versions\n(py311, and backwards-compatible)"]

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