Bump natsio/prometheus-nats-exporter in /helm/charts/nats

Bumps natsio/prometheus-nats-exporter from 0.15.0 to 0.16.0.

---
updated-dependencies:
- dependency-name: natsio/prometheus-nats-exporter
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

helm/charts/nats/values.yaml

@@ -378,7 +378,7 @@ promExporter:
   enabled: false
   image:
     repository: natsio/prometheus-nats-exporter
-    tag: 0.15.0
+    tag: 0.16.0
     pullPolicy:
     registry:
 
@@ -564,7 +564,7 @@ natsBox:
   container:
     image:
       repository: natsio/nats-box
-      tag: 0.15.0
+      tag: 0.16.0
       pullPolicy:
       registry: