migrate away from deprecated ioutil APIs (#7175)

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

test/fuzz/rpc/jsonrpc/server/fuzz_test.go

@@ -1,7 +1,7 @@
 package server_test
 
 import (
-	"io/ioutil"
+	"io"
 	"os"
 	"path/filepath"
 	"testing"
@@ -25,7 +25,7 @@ func TestServerTestdataCases(t *testing.T) {
 			}()
 			f, err := os.Open(filepath.Join(testdataCasesDir, entry.Name()))
 			require.NoError(t, err)
-			input, err := ioutil.ReadAll(f)
+			input, err := io.ReadAll(f)
 			require.NoError(t, err)
 			server.Fuzz(input)
 		})

test/fuzz/rpc/jsonrpc/server/handler.go

@@ -3,13 +3,13 @@ package server
 import (
 	"bytes"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 
 	"github.com/tendermint/tendermint/libs/log"
 	rs "github.com/tendermint/tendermint/rpc/jsonrpc/server"
-	types "github.com/tendermint/tendermint/rpc/jsonrpc/types"
+	"github.com/tendermint/tendermint/rpc/jsonrpc/types"
 )
 
 var rpcFuncMap = map[string]*rs.RPCFunc{
@@ -32,7 +32,7 @@ func Fuzz(data []byte) int {
 	rec := httptest.NewRecorder()
 	mux.ServeHTTP(rec, req)
 	res := rec.Result()
-	blob, err := ioutil.ReadAll(res.Body)
+	blob, err := io.ReadAll(res.Body)
 	if err != nil {
 		panic(err)
 	}