Remove sunsetted op_return replay protection
Summary: We now passed the sunset height, so this is not necessary anymore
Test Plan:
make check ./test/functional/test_runner.py
Reviewers: #bitcoin_abc, jasonbcox
Reviewed By: #bitcoin_abc, jasonbcox
Subscribers: teamcity
Differential Revision: https://reviews.bitcoinabc.org/D1412