fix(promtail): use default scrape config instead of incomplete override

Custom scrape_configs was missing __path__ (the actual log file path
on the node), so Promtail had no idea where to find log files.
Use chart defaults which already handle /var/log/pods/**/*.log
correctly; only set the Loki push URL.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: soohyunme

infrastructure/base/monitoring/loki/promtail-values.yaml

@@ -1,23 +1,6 @@
 config:
   clients:
     - url: http://loki:3100/loki/api/v1/push
-  scrape_configs:
-    - job_name: kubernetes-pods
-      kubernetes_sd_configs:
-        - role: pod
-      relabel_configs:
-        - source_labels: [__meta_kubernetes_pod_name]
-          action: replace
-          target_label: pod
-        - source_labels: [__meta_kubernetes_namespace]
-          action: replace
-          target_label: namespace
-        - source_labels: [__meta_kubernetes_pod_label_app]
-          action: replace
-          target_label: app
-        - source_labels: [__meta_kubernetes_pod_container_name]
-          action: replace
-          target_label: container
 
 resources:
   limits: