[backport#12204] Fix overly eager BIP30 bypass
Summary:
5b8b38775 Fix overly eager BIP30 bypass (Alex Morcos)
Pull request description:
In #6931 we introduced a possible consensus breaking change by misunderstanding how completely BIP 34 obviated the need for BIP 30. Unfixed, this could break consensus after block height about 1.9M. Explained in code comment. h/t @sdaftuar
Backport of Core PR12204
Test Plan:
ninja all check check-functional
Reviewers: #bitcoin_abc, PiRK
Reviewed By: PiRK
Differential Revision: https://reviews.bitcoinabc.org/D8209