Fix type description in Mnemonic._entropy2mnemonic
Fix type description in Mnemonic._entropy2mnemonic

bitjson/bitcore,martindale/bitcore,bitpay/bitcore,bitjson/bitcore,bitjson/bitcore,martindale/bitcore,bitpay/bitcore,bitpay/bitcore,bitjson/bitcore,martindale/bitcore,bitpay/bitcore,martindale/bitcore,bitpay/bitcore-mnemonic,bitpay/bitcore-mnemonic