build(deps): bump pytest-cov from 5.0.0 to 6.2.1 in /book/src

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 5.0.0 to 6.2.1.
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v5.0.0...v6.2.1)

---
updated-dependencies:
- dependency-name: pytest-cov
  dependency-version: 6.2.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

book/src/requirements.txt

@@ -11,7 +11,7 @@ pip-tools==7.4.1
 pyflakes==3.2.0
 pylint==3.3.7
 pytest==8.4.1
-pytest-cov==5.0.0
+pytest-cov==6.2.1
 pytype==2024.9.13
 requests==2.32.4
 yapf==0.43.0