Remove references to 'pruned' coins, which don't exist since the move
to per-txout coins db.
This is a backport of Core [[https://github.com/bitcoin/bitcoin/pull/18410 | PR18410]] [1/3]
https://github.com/bitcoin/bitcoin/pull/18410/commits/c205979031ff4e8e32a5f05bae813405f233fccd