Remove redundant parameters in various integration tests

Summary: As per title. The test framework now pases the flag forkid by default, so no need to make it explicit all over the place.

Test Plan:

./test/functional/test_runner.py --extended

Reviewers: #bitcoin_abc, schancel

Reviewed By: #bitcoin_abc, schancel

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1200