Change OS trove classifier to POSIX since our Windows support is uncertain.
Change OS trove classifier to POSIX since our Windows support is uncertain.

harrissoerja/vumi,vishwaprakashmishra/xmatrix,vishwaprakashmishra/xmatrix,vishwaprakashmishra/xmatrix,TouK/vumi,TouK/vumi,harrissoerja/vumi,harrissoerja/vumi,TouK/vumi