Clear fHavePruned in BlockManager::Unload()

-----

Code Reviewer Notes

Call graph of relevant functions:

UnloadBlockIndex() <-- Moved from
    calls ChainstateManager::Unload()
        which calls BlockManager::Unload() <-- Moved to

So calling UnloadBlockIndex() would still run this moved code. The code
will also now run when ~BlockManager gets called, which makes sense.

src/node/blockstorage.cpp

@@ -300,6 +300,8 @@ void BlockManager::Unload()
     m_last_blockfile = 0;
     m_dirty_blockindex.clear();
     m_dirty_fileinfo.clear();
+
+    fHavePruned = false;
 }
 
 bool BlockManager::WriteBlockIndexDB()

src/validation.cpp

@@ -4126,7 +4126,6 @@ void UnloadBlockIndex(CTxMemPool* mempool, ChainstateManager& chainman)
     for (int b = 0; b < VERSIONBITS_NUM_BITS; b++) {
         warningcache[b].clear();
     }
-    chainman.m_blockman.fHavePruned = false;
 }
 
 bool ChainstateManager::LoadBlockIndex()