test: Default blockversion to 4 in feature_block

Summary:
There is one tests that checks version=1 blocks are rejected. For all other tests the version doesn't matter as long as it is large enough.

This is a backport of core#20167 [2/3]
https://github.com/bitcoin/bitcoin/pull/20167/commits/fa7fb0e44241982a6e5cd560c06ac0c9d8f47f88

Test Plan: test/functional/test_runner.py feature_block

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10678