Bump mypy from 1.13.0 to 1.20.0

Bumps [mypy](https://github.com/python/mypy) from 1.13.0 to 1.20.0.
- [Changelog](https://github.com/python/mypy/blob/master/CHANGELOG.md)
- [Commits](https://github.com/python/mypy/compare/v1.13.0...v1.20.0)

---
updated-dependencies:
- dependency-name: mypy
  dependency-version: 1.20.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

pyproject.toml

@@ -15,7 +15,7 @@ dependencies = ["specklepy==3.1.0",
 
 [project.optional-dependencies]
 dev = [
-    "mypy==1.13.0",
+    "mypy==1.20.0",
     "pytest==7.4.4",
     "ruff==0.11.12",
 ]