[backport#15102] test: Run invalid_txs.InputMissing test in feature_block
Summary:
test: Run invalid_txs.InputMissing test in feature_block (MarcoFalke)
https://github.com/bitcoin/bitcoin/pull/15102/commits/fac4e731a8e5f140dc3bbca4c9af6e23fc1cd107
SegWit is _not_ active in our RegTest, so I just removed the conditional branch that refers to it.
Backport of Core PR15102
Test Plan:
ninja ./test/functional/test_runner.py feature_block
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D7318