Backport #16956
The mail template rendering was failing with the error -
`...vices/mailer/mail.go:301:composeIssueCommentMessages() [E] ExecuteTemplate [issue/default/body]: template: issue/default:65:10: executing "issue/default" at <.i18n.Tr>: can't evaluate field i18n in type *models.Comment`
The issue was the template variable i18n is available in the outer scope.
Fix#16877
Co-authored-by: 6543 <6543@obermui.de>