appveyor: upgrade mssql to 2019
appveyor: upgrade mssql to 2019

django-treebeard/django-treebeard,tabo/django-treebeard,django-treebeard/django-treebeard,tabo/django-treebeard,tabo/django-treebeard,tabo/django-treebeard,django-treebeard/django-treebeard