[#629] go.mod/spf13: Bump versions

- github.com/spf13/cast v1.3.0 => v1.3.1
- github.com/spf13/cobra v1.0.0 => v1.1.3
- github.com/spf13/viper v1.7.0 => v1.8.0

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

go.mod

@@ -18,16 +18,13 @@ require (
 	github.com/panjf2000/ants/v2 v2.3.0
 	github.com/paulmach/orb v0.2.1
 	github.com/prometheus/client_golang v1.6.0
-	github.com/spf13/cast v1.3.0
-	github.com/spf13/cobra v1.0.0
-	github.com/spf13/pflag v1.0.5 // indirect
-	github.com/spf13/viper v1.7.0
+	github.com/spf13/cast v1.3.1
+	github.com/spf13/cobra v1.1.3
+	github.com/spf13/viper v1.8.0
 	github.com/stretchr/testify v1.7.0
 	go.etcd.io/bbolt v1.3.5
 	go.uber.org/atomic v1.8.0
 	go.uber.org/zap v1.17.0
-	golang.org/x/crypto v0.0.0-20200117160349-530e935923ad // indirect
-	golang.org/x/net v0.0.0-20191105084925-a882066a44e0 // indirect
 	google.golang.org/grpc v1.38.0
 	google.golang.org/protobuf v1.26.0
 )