build(deps): bump flake8 from 7.1.2 to 7.2.0 in /book/src

Bumps [flake8](https://github.com/pycqa/flake8) from 7.1.2 to 7.2.0.
- [Commits](PyCQA/flake8@7.1.2...7.2.0)

---
updated-dependencies:
- dependency-name: flake8
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

book/src/requirements.txt

@@ -1,6 +1,6 @@
 black==24.10.0
 coverage==7.8.0
-flake8==7.1.2
+flake8==7.2.0
 hypothesis==6.130.8
 isort==5.13.2
 MutPy==0.6.1