build(deps-dev): bump mypy from 2.3.0 to 2.3.1 in /Tools

Bumps [mypy](https://github.com/python/mypy) from 2.3.0 to 2.3.1.
- [Changelog](https://github.com/python/mypy/blob/master/CHANGELOG.md)
- [Commits](python/mypy@v2.3.0...v2.3.1)

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

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

Author: dependabot[bot]

Tools/requirements-dev.txt

@@ -1,6 +1,6 @@
 # Requirements file for external linters and checks we run on
 # Tools/clinic, Tools/cases_generator/, and Tools/peg_generator/ in CI
-mypy==2.3.0
+mypy==2.3.1
 
 # needed for peg_generator:
 types-psutil==7.2.2.20260518