Remove cosmos/keyring

cosmos/keyring hasn't pulled upstream changes from 99designs/keyring yet
and the latest release of 99designs/keyring (1.2.1) appears to contain
a fix for MacOS warnings: 99designs/keyring#107

Links
- https://github.com/cosmos/keyring/tags
- https://github.com/99designs/keyring/releases/tag/v1.2.1

`make test` passes after this change and it looks like other Cosmos
chains don't need this replace:
- https://github.com/osmosis-labs/osmosis/blob/main/go.mod#L274-L285=
- https://github.com/CosmosContracts/juno/blob/main/go.mod#L178-L182=

Does anyone know if it's still necessary? I couldn't find the justification in
celestiaorg#127 which added it.

go.mod

@@ -154,7 +154,6 @@ require (
 )
 
 replace (
-	github.com/99designs/keyring => github.com/cosmos/keyring v1.1.7-0.20210622111912-ef00f8ac3d76
 	github.com/cosmos/cosmos-sdk => github.com/celestiaorg/cosmos-sdk v1.1.1-sdk-v0.46.0
 	github.com/gogo/protobuf => github.com/regen-network/protobuf v1.3.3-alpha.regen.1
 	github.com/tendermint/tendermint v0.35.4 => github.com/celestiaorg/celestia-core v1.2.4-tm-v0.35.6

go.sum

@@ -76,6 +76,8 @@ filippo.io/edwards25519 v1.0.0-rc.1 h1:m0VOOB23frXZvAOK44usCgLWvtsxIoMCTBGJZlpmG
 filippo.io/edwards25519 v1.0.0-rc.1/go.mod h1:N1IkdkCkiLB6tki+MYJoSx2JTY9NUlxZE7eHn5EwJns=
 git.sr.ht/~sircmpwn/getopt v0.0.0-20191230200459-23622cc906b3/go.mod h1:wMEGFFFNuPos7vHmWXfszqImLppbc0wEhh6JBfJIUgw=
 git.sr.ht/~sircmpwn/go-bare v0.0.0-20210406120253-ab86bc2846d9/go.mod h1:BVJwbDfVjCjoFiKrhkei6NdGcZYpkDkdyCdg1ukytRA=
+github.com/99designs/keyring v1.1.6 h1:kVDC2uCgVwecxCk+9zoCt2uEL6dt+dfVzMvGgnVcIuM=
+github.com/99designs/keyring v1.1.6/go.mod h1:16e0ds7LGQQcT59QqkTg72Hh5ShM51Byv5PEmW6uoRU=
 github.com/Antonboom/errname v0.1.5/go.mod h1:DugbBstvPFQbv/5uLcRRzfrNqKE9tVdVCqWCLp6Cifo=
 github.com/Antonboom/errname v0.1.6/go.mod h1:7lz79JAnuoMNDAWE9MeeIr1/c/VpSUWatBv2FH9NYpI=
 github.com/Antonboom/nilnil v0.1.0/go.mod h1:PhHLvRPSghY5Y7mX4TW+BHZQYo1A8flE5H20D3IPZBo=
@@ -336,8 +338,6 @@ github.com/cosmos/gorocksdb v1.2.0 h1:d0l3jJG8M4hBouIZq0mDUHZ+zjOx044J3nGRskwTb4
 github.com/cosmos/gorocksdb v1.2.0/go.mod h1:aaKvKItm514hKfNJpUJXnnOWeBnk2GL4+Qw9NHizILw=
 github.com/cosmos/iavl v0.18.0 h1:02ur4vnalMR2GuWCFNkuseUcl/BCVmg9tOeHOGiZOkE=
 github.com/cosmos/iavl v0.18.0/go.mod h1:L0VZHfq0tqMNJvXlslGExaaiZM7eSm+90Vh9QUbp6j4=
-github.com/cosmos/keyring v1.1.7-0.20210622111912-ef00f8ac3d76 h1:DdzS1m6o/pCqeZ8VOAit/gyATedRgjvkVI+UCrLpyuU=
-github.com/cosmos/keyring v1.1.7-0.20210622111912-ef00f8ac3d76/go.mod h1:0mkLWIoZuQ7uBoospo5Q9zIpqq6rYCPJDSUdeCJvPM8=
 github.com/cosmos/ledger-cosmos-go v0.11.1 h1:9JIYsGnXP613pb2vPjFeMMjBI5lEDsEaF6oYorTy6J4=
 github.com/cosmos/ledger-cosmos-go v0.11.1/go.mod h1:J8//BsAGTo3OC/vDLjMRFLW6q0WAaXvHnVc7ZmE8iUY=
 github.com/cosmos/ledger-go v0.9.2 h1:Nnao/dLwaVTk1Q5U9THldpUMMXU94BOTWPddSmVB6pI=