[prometheus-nginx-exporter] Update Helm release nginx to v21.1.21 (#6060)

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

Author: renovate[bot]

charts/prometheus-nginx-exporter/Chart.lock

@@ -1,6 +1,6 @@
 dependencies:
 - name: nginx
   repository: https://charts.bitnami.com/bitnami
-  version: 21.1.16
-digest: sha256:e4e87350eb43903462e8f2a492e673e6ebc3aec75143df8cc4927a6fc481436e
-generated: "2025-08-15T10:01:32.967796743Z"
+  version: 21.1.21
+digest: sha256:3563f9b6cc31ed2c0264b19baf8a9a0718365f94168bf02a43d512e652a6170e
+generated: "2025-08-15T18:01:33.791312043Z"

charts/prometheus-nginx-exporter/Chart.yaml

@@ -2,7 +2,7 @@
 apiVersion: v2
 description: A Helm chart for NGINX Prometheus Exporter
 name: prometheus-nginx-exporter
-version: 1.11.6
+version: 1.11.7
 # renovate: github-releases=nginx/nginx-prometheus-exporter
 appVersion: 1.4.2
 home: https://github.com/nginxinc/nginx-prometheus-exporter
@@ -33,6 +33,6 @@ annotations:
 type: application
 dependencies:
   - name: nginx
-    version: "21.1.16"
+    version: "21.1.21"
     repository: https://charts.bitnami.com/bitnami
     condition: nginx.enabled