Fix version in APIv1 deprecation notice (prometheus#3815)

Signed-off-by: George Robinson <george.robinson@grafana.com>

api/api.go

@@ -162,7 +162,7 @@ func New(opts Options) (*API, error) {
 // true for the concurrency limit, with the exception that it is only applied to
 // GET requests.
 func (api *API) Register(r *route.Router, routePrefix string) *http.ServeMux {
-	// TODO(gotjosh) API V1 was removed as of version 0.28, when we reach 1.0.0 we should removed these deprecation warnings.
+	// TODO(gotjosh) API V1 was removed as of version 0.27, when we reach 1.0.0 we should removed these deprecation warnings.
 	api.deprecationRouter.Register(r.WithPrefix("/api/v1"))
 
 	mux := http.NewServeMux()

api/metrics/metrics.go

@@ -23,7 +23,7 @@ type Alerts struct {
 }
 
 // NewAlerts returns an *Alerts struct for the given API version.
-// Since v1 was deprecated in 0.28, v2 is now hardcoded.
+// Since v1 was deprecated in 0.27, v2 is now hardcoded.
 func NewAlerts(r prometheus.Registerer) *Alerts {
 	numReceivedAlerts := prometheus.NewCounterVec(prometheus.CounterOpts{
 		Name:        "alertmanager_alerts_received_total",

api/v1_deprecation_router.go

@@ -54,7 +54,7 @@ func (dr *V1DeprecationRouter) deprecationHandler(w http.ResponseWriter, req *ht
 		Error  string `json:"error"`
 	}{
 		"deprecated",
-		"The Alertmanager v1 API was deprecated in version 0.16.0 and is removed as of version 0.28.0 - please use the equivalent route in the v2 API",
+		"The Alertmanager v1 API was deprecated in version 0.16.0 and is removed as of version 0.27.0 - please use the equivalent route in the v2 API",
 	}
 
 	w.Header().Set("Content-Type", "application/json")