[Cleanup][Wallet] Don't count zPIV in MintableCoins()
[Cleanup][Wallet] Don't count zPIV in MintableCoins()

zPIV are not stakeable anymore. They shouldn't be counted here.
Mrs-X/Darknet,Mrs-X/Darknet,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,Mrs-X/Darknet,Darknet-Crypto/Darknet,Mrs-X/PIVX,PIVX-Project/PIVX,Darknet-Crypto/Darknet,Darknet-Crypto/Darknet,PIVX-Project/PIVX,Darknet-Crypto/Darknet,Mrs-X/Darknet,Mrs-X/PIVX,PIVX-Project/PIVX,Mrs-X/PIVX,PIVX-Project/PIVX,Mrs-X/PIVX,Mrs-X/Darknet,Mrs-X/PIVX,Darknet-Crypto/Darknet,Mrs-X/Darknet,Darknet-Crypto/Darknet,Mrs-X/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX