chore(deps): update grafana/otel-lgtm docker tag to v0.21.0 (#1053)

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

Author: renovate[bot]

logging-k8s-stdout-otlp-json/k8s/lgtm.yaml

@@ -47,7 +47,7 @@ spec:
     spec:
       containers:
         - name: lgtm
-          image: grafana/otel-lgtm:0.20.0@sha256:d3683fa0629ad8c8ab20230657637600aeb42141975e635bab3299b28e5a49c0
+          image: grafana/otel-lgtm:0.21.0@sha256:ab627177ef1c209f4e17261401bb6649477de739a17e69a23a419b8d91d03b2f
           ports:
             - containerPort: 3000
             - containerPort: 4317