chore(deps): update precommit hook pycqa/flake8 to v3.9.0 (#52)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [pycqa/flake8](https://gitlab.com/pycqa/flake8) | repository | minor | `3.8.4` -> `3.9.0` |

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### Release Notes

<details>
<summary>pycqa/flake8</summary>

### [`v3.9.0`](https://gitlab.com/pycqa/flake8/compare/3.8.4...3.9.0)

[Compare Source](https://gitlab.com/pycqa/flake8/compare/3.8.4...3.9.0)

</details>

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:recycle: **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

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 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

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.pre-commit-config.yaml

@@ -12,6 +12,6 @@ repos:
     hooks:
     - id: black
 -   repo: https://gitlab.com/pycqa/flake8
-    rev: 3.8.4
+    rev: 3.9.0
     hooks:
     - id: flake8