Avoid spurious BIP30 error in DB consistency checks

Solve a spurious warning generated during fine-grained consensus checks.
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22596

Bitcoin Issue

Days

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$3,750.00

Paid in USD or equivalent BTC upon acceptance

Bitcoin Issue

In `validation.cpp:ConnectBlock()`, duplicate coinbase transactions are accounted for per BIP30. However in `validation.cpp:DisconnectBlock()` there is no such special handling, which causes issues at the two affected blocks when using a high `checklevel=` setting.

Fix `DisconnectBlock()` to account for BIP30 and avoid the related spurious VerifyDB() failures.

See this comment in particular.

Prerequisite Skills

C++

Code Guidelines

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Definition of Done

Get a PR merged which closes the original issue

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