[api] Bump pytest-mock from 3.14.1 to 3.15.1 in /backend

Bumps [pytest-mock](https://github.com/pytest-dev/pytest-mock) from 3.14.1 to 3.15.1.
- [Release notes](https://github.com/pytest-dev/pytest-mock/releases)
- [Changelog](https://github.com/pytest-dev/pytest-mock/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-mock@v3.14.1...v3.15.1)

---
updated-dependencies:
- dependency-name: pytest-mock
  dependency-version: 3.15.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

backend/poetry.lock

@@ -24,7 +24,7 @@ tomli = "^2.2.1"
 pylint = "^3.3.8"
 isort = "^6.0.1"
 pytest = "^8.4.1"
-pytest-mock = "^3.14.1"
+pytest-mock = "^3.15.1"
 pytest-cov = "^6.2.1"
 
 [build-system]