Fix indexer chart autoscaling

It was using the an inexistant target to autoscale

Refs. swh/infra/sysadm-environment#4810

swh/templates/indexers/keda-autoscaling.yaml

 {{ if .Values.indexers.enabled -}}
 {{- range $indexer_type, $deployment_config := .Values.indexers.deployments -}}
+{{- $indexer_name := ( print "indexer-" $indexer_type ) -}}
 {{- $autoscalingConfig := get $deployment_config "autoScaling" -}}
 {{ if $autoscalingConfig }}
 {{- $journalUser := $.Values.indexers.journalBrokers.user -}}
@@ -12,7 +13,7 @@ metadata:
   namespace: {{ $.Values.namespace }}
 spec:
   scaleTargetRef:
-    name: indexer-{{ $indexer_type }}
+    name: {{ $indexer_name }}
   pollingInterval: {{ get $autoscalingConfig "poolInterval" | default 120 }}
   minReplicaCount: {{ get $autoscalingConfig "minReplicaCount" | default 1 }}
   maxReplicaCount: {{ get $autoscalingConfig "maxReplicaCount" | default 5 }}