Update Helm release nats/nats to v2.12.6 (#1719)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

examples/nats.yaml

@@ -10,7 +10,7 @@ spec:
   - repositoryURL:    https://nats-io.github.io/k8s/helm/charts/
     repositoryName:   nats
     chartName:        nats/nats
-    chartVersion:     2.12.4
+    chartVersion:     2.12.6
     releaseName:      nats
     releaseNamespace: nats
     helmChartAction:  Install