Update mypy requirement from >=0.991,<1.5 to >=0.991,<1.6

Updates the requirements on [mypy](https://github.com/python/mypy) to permit the latest version.
- [Commits](python/mypy@v0.991...v1.5.0)

---
updated-dependencies:
- dependency-name: mypy
  dependency-type: direct:development
...

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

pyproject.toml

@@ -26,7 +26,7 @@ typing-extensions = "^4.4.0"
 pre-commit = "^2.20.0"
 Pillow = ">=9.3,<11.0"
 CairoSVG = "^2.5.2"
-mypy = ">=0.991,<1.5"
+mypy = ">=0.991,<1.6"
 
 [build-system]
 requires = ["poetry-core"]