doc: Install net/py-pyzmq port on FreeBSD for interface_zmq.py

Author: hebasto

doc/build-freebsd.md

@@ -96,7 +96,7 @@ There is an included test suite that is useful for testing code changes when dev
 To run the test suite (recommended), you will need to have Python 3 installed:
 
 ```bash
-pkg install python3 databases/py-sqlite3
+pkg install python3 databases/py-sqlite3 net/py-pyzmq
 ```
 ---