fix tenant labels (#468)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Updated the HelmRelease configuration for monitoring agents to
simplify tenant label assignment by using the release namespace
directly.
  
- **Bug Fixes**
- Adjusted the logging configuration for `fluent-bit` to ensure accurate
categorization and processing of monitoring data.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/apps/kubernetes/templates/helmreleases/monitoring-agents.yaml

@@ -45,7 +45,7 @@ spec:
     vmagent:
       externalLabels:
         cluster: {{ .Release.Name }}
-        tenant: {{ $targetTenant }}
+        tenant: {{ .Release.Namespace }}
       remoteWrite:
         url: http://vminsert-shortterm.{{ $targetTenant }}.svc:8480/insert/0/prometheus
 
@@ -97,7 +97,7 @@ spec:
           [FILTER]
               Name modify
               Match *
-              Add tenant {{ $targetTenant }}
+              Add tenant {{ .Release.Namespace }}
           [FILTER]
               Name modify
               Match *