Extend to mypy<0.970 (#725)

Author: adrianeboyd

requirements.txt

@@ -22,7 +22,7 @@ pytest-cov>=2.7.0,<2.8.0
 coverage>=5.0.0,<6.0.0
 mock>=2.0.0,<3.0.0
 flake8>=3.5.0,<3.6.0
-mypy>=0.901,<0.960; platform_machine!='aarch64'
+mypy>=0.901,<0.970; platform_machine!='aarch64'
 types-mock>=0.1.1
 types-contextvars>=0.1.2; python_version < "3.7"
 types-dataclasses>=0.1.3; python_version < "3.7"