Tests for 'windows-latest' and conda packages for win-64 were removed from GitHub workflows

[dprada]

Due to a problem with the package of OpenMM for windows reported in openmm/openmm#3618 (comment), Tests for 'windows-latest' and the production of conda packages for win-64 were removed from the GitHub workflows in version 6.0.1. We should check if this is solved in the future. If PyUnitWizard can not work with windows, dependants such as MolSysMT either.