replace p2p with p2ps[0] in p2p_invalid_tx
Summary:
This is a backport of core#19804 [3/4]
https://github.com/bitcoin/bitcoin/pull/19804/commits/549d30faf04612d9589c81edf9770c99e3221885
Test Plan: test/functional/test_runner.py p2p_invalid_tx
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D10324