audio/ecasound: Update to 2.9.3

Minor release with some bugfixes. Most important change
is full support for Python 3 now.

Changelog: https://nosignal.fi/ecasound/history.php

PR: 251521
Submitted by: Neel Chauhan <neel@neelc.org> (maintainer)
Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D27491