Update dependencies (#1851)

vendor/github.com/slack-go/slack/internal/misc/misc.go

@@ -1,28 +0,0 @@
-package misc
-
-import (
-	"fmt"
-	"net/http"
-)
-
-// StatusCodeError represents an http response error.
-// type httpStatusCode interface { HTTPStatusCode() int } to handle it.
-type StatusCodeError struct {
-	Code   int
-	Status string
-}
-
-func (t StatusCodeError) Error() string {
-	return fmt.Sprintf("slack server error: %s", t.Status)
-}
-
-func (t StatusCodeError) HTTPStatusCode() int {
-	return t.Code
-}
-
-func (t StatusCodeError) Retryable() bool {
-	if t.Code >= 500 || t.Code == http.StatusTooManyRequests {
-		return true
-	}
-	return false
-}