Call ReallocateCache() on each Flush()

This frees up all associated memory with the map, not only the nodes.
This is necessary in preparation for using the PoolAllocator for
CCoinsMap, which does not actually free any memory on clear().

src/validation.cpp

@@ -4930,7 +4930,6 @@ bool Chainstate::ResizeCoinsCaches(size_t coinstip_size, size_t coinsdb_size)
     } else {
         // Otherwise, flush state to disk and deallocate the in-memory coins map.
         ret = FlushStateToDisk(state, FlushStateMode::ALWAYS);
-        CoinsTip().ReallocateCache();
     }
     return ret;
 }