wallet: Remove unnecessary mempool lock in ReacceptWalletTransactions

zcash: cherry picked from commit 5b25293
zcash: bitcoin/bitcoin#11870

src/wallet/wallet.cpp

@@ -2850,11 +2850,8 @@ void CWallet::ReacceptWalletTransactions()
     }
 
     // Try to add wallet transactions to memory pool
-    for (std::pair<const int64_t, CWalletTx*>& item : mapSorted)
-    {
+    for (std::pair<const int64_t, CWalletTx*>& item : mapSorted) {
         CWalletTx& wtx = *(item.second);
-
-        LOCK(mempool.cs);
         wtx.AcceptToMemoryPool(false);
     }
 }