Run gopls modernize on codebase (#34751)

Recent modernize fixes:
https://github.com/golang/tools/commits/master/gopls/internal/analysis/modernize

services/migrations/github.go

@@ -89,8 +89,8 @@ func NewGithubDownloaderV3(_ context.Context, baseURL, userName, password, token
 	}
 
 	if token != "" {
-		tokens := strings.Split(token, ",")
-		for _, token := range tokens {
+		tokens := strings.SplitSeq(token, ",")
+		for token := range tokens {
 			token = strings.TrimSpace(token)
 			ts := oauth2.StaticTokenSource(
 				&oauth2.Token{AccessToken: token},