chore(deps): update grafana/promtail docker tag to v2.9.15

Author: renovate[bot]

build-images.sh

@@ -10,7 +10,7 @@ repobase="${REPOBASE:-ghcr.io/nethserver}"
 # Configure the image name
 reponame="nethsecurity-controller"
 controller_version="2.0.0"
-promtail_image="docker.io/grafana/promtail:2.7.1"
+promtail_image="docker.io/grafana/promtail:2.9.15"
 loki_image="docker.io/grafana/loki:2.9.15"
 prometheus_image="docker.io/prom/prometheus:v2.50.1"
 grafana_image="docker.io/grafana/grafana:12.0.2"