Merge bitcoin/bitcoin#31535: doc: Install py3-zmq port on OpenBSD for interface_zmq.py

be1a2e5 doc: Install `py3-zmq` port on OpenBSD for `interface_zmq.py` (Hennadii Stepanov)

Pull request description:

  On OpenBSD, Python's `zmq` module is provided as a separate [port](https://www.ports.to/path/net/py-zmq,python3.html).

  This PR updates the OpenBSD Build Guide to include this port, enabling the `interface_zmq.py` functional test.

  Also updates the documented OpenBSD version.

ACKs for top commit:
  theStack:
    Tested ACK be1a2e5

Tree-SHA512: 4d560385b94e8c7491aa19d2157d8a799617e08136601dc565a909d4c74e12582a1d273bc97ad7c2d0e57c5cf7377560ba02ef58c12f8991652322553740d2ba

Author: fanquake

doc/build-openbsd.md

@@ -1,6 +1,6 @@
 # OpenBSD Build Guide
 
-**Updated for OpenBSD [7.5](https://www.openbsd.org/75.html)**
+**Updated for OpenBSD [7.6](https://www.openbsd.org/76.html)**
 
 This guide describes how to build bitcoind, command-line utilities, and GUI on OpenBSD.
 
@@ -90,7 +90,7 @@ 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_add python  # Select the newest version of the package.
+pkg_add python py3-zmq  # Select the newest version of the python package if necessary.
 ```
 
 ## Building Bitcoin Core