migrate away from deprecated ioutil APIs (#7175)

Co-authored-by: Callum Waters <cmwaters19@gmail.com>
Co-authored-by: M. J. Fromberger <fromberger@interchain.io>

internal/state/state.go

@@ -4,7 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"os"
 	"time"
 
 	"github.com/gogo/protobuf/proto"
@@ -323,7 +323,7 @@ func MakeGenesisStateFromFile(genDocFile string) (State, error) {
 
 // MakeGenesisDocFromFile reads and unmarshals genesis doc from the given file.
 func MakeGenesisDocFromFile(genDocFile string) (*types.GenesisDoc, error) {
-	genDocJSON, err := ioutil.ReadFile(genDocFile)
+	genDocJSON, err := os.ReadFile(genDocFile)
 	if err != nil {
 		return nil, fmt.Errorf("couldn't read GenesisDoc file: %v", err)
 	}