The nil check before the range loop is redundant

Signed-off-by: Rijnard van Tonder <hi.teresy@gmail.com>

discovery/gce/gce.go

@@ -244,12 +244,10 @@ func (d *Discovery) refresh() (tg *targetgroup.Group, err error) {
 			}
 
 			// GCE labels are key-value pairs that group associated resources
-			if inst.Labels != nil {
 			for key, value := range inst.Labels {
 				name := strutil.SanitizeLabelName(key)
 				labels[gceLabelLabel+model.LabelName(name)] = model.LabelValue(value)
 			}
-			}
 
 			if len(priIface.AccessConfigs) > 0 {
 				ac := priIface.AccessConfigs[0]