Update quay.io/prometheus/node-exporter Docker tag to v1.8.1 (#154)

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

Author: renovate[bot]

manifests/monitoring/node-exporter.yaml

@@ -48,7 +48,7 @@ spec:
       serviceAccountName: prometheus-node-exporter
       containers:
         - name: prometheus-node-exporter
-          image: "quay.io/prometheus/node-exporter:v1.8.0"
+          image: "quay.io/prometheus/node-exporter:v1.8.1"
           imagePullPolicy: "IfNotPresent"
           args:
             - --web.listen-address=:9100