tests: Use MakeUnique to construct objects owned by unique_ptrs

src/wallet/test/coinselector_tests.cpp

@@ -65,7 +65,7 @@ static void add_coin(const CAmount& nValue, int nAge = 6*24, bool fIsFromMe = fa
         // so stop vin being empty, and cache a non-zero Debit to fake out IsFromMe()
         tx.vin.resize(1);
     }
-    std::unique_ptr<CWalletTx> wtx(new CWalletTx(&testWallet, MakeTransactionRef(std::move(tx))));
+    std::unique_ptr<CWalletTx> wtx = MakeUnique<CWalletTx>(&testWallet, MakeTransactionRef(std::move(tx)));
     if (fIsFromMe)
     {
         wtx->fDebitCached = true;