change test mail subject and body to 'Gitea Test Mail!'

Signed-off-by: Michael de Wit <mjwwit@gmail.com>

models/mail.go

@@ -40,7 +40,7 @@ func InitMailRender(tmpls *template.Template) {
 
 // SendTestMail sends a test mail
 func SendTestMail(email string) error {
-	return gomail.Send(&mailer.Sender{}, mailer.NewMessage([]string{email}, "Gogs Test Email!", "Gogs Test Email!").Message)
+	return gomail.Send(&mailer.Sender{}, mailer.NewMessage([]string{email}, "Gitea Test Email!", "Gitea Test Email!").Message)
 }
 
 // SendUserMail sends a mail to the user