Bump windows CI to windows-2019
Bump windows CI to windows-2019

The previous version, vs2017-win2016, is being removed today. Bump the
version to windows-2019.

Signed-off-by: Patrick Avery <743342299f279e7a8c3ff5eb40671fce3e95f13a@kitware.com>

OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz