Removes dead code from after the generate method was removed
https://github.com/bitcoin/bitcoin/pull/15492748/commits/8bb3e4c487500a580e3e18791b1f4e7dcdd354429819ad6d07097ca4df92231e18de0b57313e3b78
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Depends on D6710
Partial backport of Core [[https://github.com/bitcoin/bitcoin/pull/15492748 | PR15492748]]