Alerting: Fix OK state doesn't show up in Microsoft Teams (#11032)

* Alerting: Fix OK state doesn't show up in Microsoft Teams

* Fix formatting

pkg/services/alerting/notifiers/teams.go

@@ -82,6 +82,8 @@ func (this *TeamsNotifier) Notify(evalContext *alerting.EvalContext) error {
 	message := this.Mention
 	if evalContext.Rule.State != m.AlertStateOK { //dont add message when going back to alert state ok.
 		message += " " + evalContext.Rule.Message
+	} else {
+		message += " " // summary must not be empty
 	}
 
 	body := map[string]interface{}{