dev-requirements-windows: remove cov-core which is part of pytest-cov
dev-requirements-windows: remove cov-core which is part of pytest-cov

https://github.com/schlamar/cov-core

jhamrick/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,jupyter/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,jupyter/nbgrader,jupyter/nbgrader,jhamrick/nbgrader