style(keys): remove unused code buy key (#253)

Makefile

@@ -147,7 +147,7 @@ lint: lint-install
 	echo "--> Running linter"
 	$(MAKE) lint-install
 	@golangci-lint run --build-tags=$(GO_BUILD) --out-format=tab
-	@if [ $$(find . -name '*.go' -type f | xargs grep 'nolint\|#nosec' | wc -l) -ne 40 ]; then \
+	@if [ $$(find . -name '*.go' -type f | xargs grep 'nolint\|#nosec' | wc -l) -ne 38 ]; then \
 		echo "--> increase or decrease nolint, please recheck them"; \
 		echo "--> list nolint: \`find . -name '*.go' -type f | xargs grep 'nolint\|#nosec'\`"; exit 1;\
 	fi

x/crosschain/types/key.go

@@ -90,7 +90,7 @@ var (
 	LastEventBlockHeightByOracleKey = []byte{0x35}
 
 	// Deprecated: PastExternalSignatureCheckpointKey indexes eth signature checkpoints that have existed
-	PastExternalSignatureCheckpointKey = []byte{0x36}
+	// PastExternalSignatureCheckpointKey = []byte{0x36}
 
 	// LastOracleSlashBlockHeight indexes the last oracle slash block height
 	LastOracleSlashBlockHeight = []byte{0x37}
@@ -104,8 +104,8 @@ var (
 	// ParamsKey is the prefix for params key
 	ParamsKey = []byte{0x40}
 
-	// OutgoingTxRelationKey outgoing tx with evm
-	OutgoingTxRelationKey = []byte{0x41}
+	// Deprecated: OutgoingTxRelationKey outgoing tx with evm
+	// OutgoingTxRelationKey = []byte{0x41}
 
 	BridgeCallRefundKey = []byte{0x42}
 
@@ -198,15 +198,6 @@ func GetTokenToDenomKey(denom string) []byte {
 	return append(TokenToDenomKey, []byte(denom)...)
 }
 
-// GetPastExternalSignatureCheckpointKey returns the following key format
-func GetPastExternalSignatureCheckpointKey(blockHeight uint64, checkpoint []byte) []byte {
-	return append(PastExternalSignatureCheckpointKey, append(sdk.Uint64ToBigEndian(blockHeight), checkpoint...)...)
-}
-
-func GetOutgoingTxRelationKey(txID uint64) []byte {
-	return append(OutgoingTxRelationKey, sdk.Uint64ToBigEndian(txID)...)
-}
-
 func GetBridgeCallRefundKey(address string, nonce uint64) []byte {
 	return append(BridgeCallRefundKey, append([]byte(address), sdk.Uint64ToBigEndian(nonce)...)...)
 }