[validation] Remove pool member from ConnectTrace

It's no longer used for anything.

src/validation.cpp

@@ -2517,10 +2517,9 @@ struct PerBlockConnectTrace {
 class ConnectTrace {
 private:
     std::vector<PerBlockConnectTrace> blocksConnected;
-    CTxMemPool &pool;
 
 public:
-    explicit ConnectTrace(CTxMemPool &_pool) : blocksConnected(1), pool(_pool) {}
+    explicit ConnectTrace() : blocksConnected(1) {}
 
     void BlockConnected(CBlockIndex* pindex, std::shared_ptr<const CBlock> pblock) {
         assert(!blocksConnected.back().pindex);
@@ -2833,7 +2832,7 @@ bool CChainState::ActivateBestChain(BlockValidationState &state, const CChainPar
             do {
                 // We absolutely may not unlock cs_main until we've made forward progress
                 // (with the exception of shutdown due to hardware issues, low disk space, etc).
-                ConnectTrace connectTrace(mempool); // Destructed before cs_main is unlocked
+                ConnectTrace connectTrace; // Destructed before cs_main is unlocked
 
                 if (pindexMostWork == nullptr) {
                     pindexMostWork = FindMostWorkChain();