Use cosmos' fork of github.com/bartekn/go-bip39 (cosmos#5867)

Thanks @fedekunze for pointing this out.

client/keys/add.go

@@ -8,7 +8,7 @@ import (
 	"io"
 	"sort"
 
-	bip39 "github.com/bartekn/go-bip39"
+	bip39 "github.com/cosmos/go-bip39"
 
 	"github.com/cosmos/cosmos-sdk/client/flags"
 	"github.com/cosmos/cosmos-sdk/client/input"

client/keys/mnemonic.go

@@ -5,7 +5,7 @@ import (
 	"crypto/sha256"
 	"fmt"
 
-	bip39 "github.com/bartekn/go-bip39"
+	bip39 "github.com/cosmos/go-bip39"
 	"github.com/spf13/cobra"
 
 	"github.com/cosmos/cosmos-sdk/client/input"

go.mod

@@ -2,7 +2,6 @@ module github.com/cosmos/cosmos-sdk
 
 require (
 	github.com/99designs/keyring v1.1.4
-	github.com/bartekn/go-bip39 v0.0.0-20171116152956-a05967ea095d
 	github.com/bgentry/speakeasy v0.1.0
 	github.com/btcsuite/btcd v0.0.0-20190115013929-ed77733ec07d
 	github.com/cosmos/go-bip39 v0.0.0-20180819234021-555e2067c45d

go.sum

@@ -29,8 +29,6 @@ github.com/aryann/difflib v0.0.0-20170710044230-e206f873d14a/go.mod h1:DAHtR1m6l
 github.com/aws/aws-lambda-go v1.13.3/go.mod h1:4UKl9IzQMoD+QF79YdCuzCwp8VbmG4VAQwij/eHl5CU=
 github.com/aws/aws-sdk-go v1.27.0/go.mod h1:KmX6BPdI08NWTb3/sm4ZGu5ShLoqVDhKgpiN924inxo=
 github.com/aws/aws-sdk-go-v2 v0.18.0/go.mod h1:JWVYvqSMppoMJC0x5wdwiImzgXTI9FuZwxzkQq9wy+g=
-github.com/bartekn/go-bip39 v0.0.0-20171116152956-a05967ea095d h1:1aAija9gr0Hyv4KfQcRcwlmFIrhkDmIj2dz5bkg/s/8=
-github.com/bartekn/go-bip39 v0.0.0-20171116152956-a05967ea095d/go.mod h1:icNx/6QdFblhsEjZehARqbNumymUT/ydwlLojFdv7Sk=
 github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=