chore(deps): update prom/memcached-exporter docker tag to v0.15.3

Author: renovate[bot]

production/helm/loki/values.yaml

@@ -3215,7 +3215,7 @@ memcachedExporter:
   enabled: true
   image:
     repository: prom/memcached-exporter
-    tag: v0.15.2
+    tag: v0.15.3
     pullPolicy: IfNotPresent
   resources:
     requests: {}