Fix mypy in CI?

Author: jmchilton

tox.ini

@@ -20,7 +20,7 @@ commands =
     lint: black --check --diff .
     lintdocs: make lint-docs
     lintdocstrings: flake8 gxformat2
-    mypy: make mypy
+    mypy: MYPYPATH=mypy-stubs mypy gxformat2
     unit: pytest {posargs}
     iwc: pytest tests/test_lint.py::TestIWCLint tests/test_pydantic_schema.py::TestIWCPydantic tests/test_native_schema.py::TestIWCWorkflows -x {posargs}
 passenv =