fix allowed change ref types environment read

change the name of the variable in the if clause for the one that contains the env  values.
Follow the same approach that with other Env Variables

Author: aoteropas

jenkins/webhook-proxy/main.go

@@ -204,7 +204,7 @@ func main() {
 
 	var allowedChangeRefTypes []string
 	envAllowedChangeRefTypes := strings.ToLower(os.Getenv(allowedChangeRefTypesEnvVar))
-	if len(allowedChangeRefTypes) == 0 {
+	if len(envAllowedChangeRefTypes) == 0 {
 		allowedChangeRefTypes = strings.Split(allowedChangeRefTypesDefault, ",")
 		log.Println(
 			"INFO:",