⬆ bump mypy from 1.20.2 to 2.3.1

Bumps [mypy](https://github.com/python/mypy) from 1.20.2 to 2.3.1.
- [Changelog](https://github.com/python/mypy/blob/master/CHANGELOG.md)
- [Commits](python/mypy@v1.20.2...v2.3.1)

---
updated-dependencies:
- dependency-name: mypy
  dependency-version: 2.3.1
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

backend/pyproject.toml

@@ -35,7 +35,7 @@ dependencies = [
 [dependency-groups]
 dev = [
     "pytest>=9.0.3,<10.0.0",
-    "mypy<2.0.0,>=1.8.0",
+    "mypy>=2.3.1,<3.0.0",
     "ruff>=0.16.0,<1.0.0",
     "prek>=0.2.24,<1.0.0",
     "coverage>=7.15.0,<8.0.0",