Update dependencies (#1813)

vendor/github.com/bwmarrin/discordgo/util.go

@@ -2,7 +2,6 @@ package discordgo
 
 import (
 	"bytes"
-	"encoding/json"
 	"fmt"
 	"io"
 	"mime/multipart"
@@ -30,7 +29,7 @@ func MultipartBodyWithJSON(data interface{}, files []*File) (requestContentType
 	body := &bytes.Buffer{}
 	bodywriter := multipart.NewWriter(body)
 
-	payload, err := json.Marshal(data)
+	payload, err := Marshal(data)
 	if err != nil {
 		return
 	}