fix #4136: revert to extras_require
fix #4136: revert to extras_require

fujicoin/electrum-fjc,pooler/electrum-ltc,pooler/electrum-ltc,asfin/electrum,cryptapus/electrum,cryptapus/electrum,wakiyamap/electrum-mona,spesmilo/electrum,vialectrum/vialectrum,spesmilo/electrum,neocogent/electrum,vialectrum/vialectrum,spesmilo/electrum,kyuupichan/electrum,fujicoin/electrum-fjc,asfin/electrum,kyuupichan/electrum,vialectrum/vialectrum,spesmilo/electrum,pooler/electrum-ltc,fujicoin/electrum-fjc,wakiyamap/electrum-mona,neocogent/electrum,pooler/electrum-ltc,wakiyamap/electrum-mona,kyuupichan/electrum,neocogent/electrum,asfin/electrum,wakiyamap/electrum-mona,cryptapus/electrum