chore(pre-commit): remove flake8 hook (#5324)

Problem
- flake8 is redundant with ruff in pre-commit and adds extra
dependency/latency.

Change
- Remove the flake8 repo hook from .pre-commit-config.yaml.

Authored by OpenClaw (model: gpt-5.2)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Removed Flake8 linting tool from the development pre-commit pipeline.
This change reduces external dependencies and maintenance overhead for
developers. The pre-commit pipeline continues to function normally with
other configured quality checks remaining active.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: njzjz-bot

.pre-commit-config.yaml

@@ -39,14 +39,6 @@ repos:
       - id: ruff-format
         exclude: ^source/3rdparty
         types_or: [python, pyi, jupyter]
-  - repo: https://github.com/pycqa/flake8
-    # flake8 cannot autofix
-    rev: "7.3.0"
-    hooks:
-      - id: flake8
-        additional_dependencies:
-          - torchfix==0.7.0
-          - flake8-pyproject==1.2.3
   # numpydoc
   - repo: https://github.com/Carreau/velin
     rev: 0.0.12