[Util] Remove a duplicate variable definition

Author: Warrows

src/chainparams.cpp

@@ -189,7 +189,6 @@ class CMainParams : public CChainParams
         nMasternodeCountDrift = 20;
         nMaxMoneyOut = 21000000 * COIN;
         nMinColdStakingAmount = 1 * COIN;
-        nTimeSlotLength = 15;           // 15 seconds
 
         /** Height or Time Based Activations **/
         nLastPOWBlock = 259200;