Bump twisted from 15.4.0 to 19.2.1 in /app/udpserver
Bump twisted from 15.4.0 to 19.2.1 in /app/udpserver

Bumps [twisted](https://github.com/twisted/twisted) from 15.4.0 to 19.2.1.
- [Release notes](https://github.com/twisted/twisted/releases)
- [Changelog](https://github.com/twisted/twisted/blob/twisted-19.2.1/NEWS.rst)
- [Commits](https://github.com/twisted/twisted/compare/twisted-15.4.0...twisted-19.2.1)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
palfrey/pyrexia,palfrey/pyrexia,palfrey/pyrexia,palfrey/pyrexia,palfrey/pyrexia,palfrey/pyrexia