Alerting: Update replacement of prometheus-alertmanager (#56519)

grafana.com/grafana/prometheus-alertmanager has been updated to a
version that fixes some bugs upstream. This change just updates that
dependency and a few shared ones.

pkg/services/ngalert/notifier/channels/telegram_test.go

@@ -93,7 +93,7 @@ func TestTelegramNotifier(t *testing.T) {
 			},
 			expMsg: map[string]string{
 				"parse_mode": "html",
-				"text":       strings.Repeat("1", 4096-3) + "...",
+				"text":       strings.Repeat("1", 4096-1) + "…",
 			},
 			expMsgError: nil,
 		}, {