Fix compacting headers

Use the compaction threshold instead of the latest block header height
to calculate which headers we will need to copy over based on the
minimum block header history.

Fixes compaction-tests locally.

Author: edmundnoble

src/Chainweb/Pact/Backend/Compaction.hs

@@ -771,7 +771,7 @@ compactRocksDb logger cwVersion cids minBlockHeight srcDb targetDb = do
 
         Just minBlockHeaderHistory -> do
           let runBack =
-                let x = int latestHeader
+                let x = int minBlockHeight
                     y = minBlockHeaderHistory
                 in if x >= y then x - y else 0
           iterSeek it $ RankedBlockHash (BlockHeight runBack) nullBlockHash