Trivy: Document Vulnerability Observability (#99414)

We use Vulnerability Observability for Docker images. The current comments say we simply don't scan them at all, so
let's make it clear for future readers that we do, in fact, scan Docker images, too.

.github/workflows/trivy-scan.yml

@@ -27,11 +27,14 @@ jobs:
         trivy fs --no-progress --download-db-only --db-repository public.ecr.aws/aquasecurity/trivy-db
     - name: Run Trivy vulnerability scanner (table output)
       # Use the trivy binary rather than the aquasecurity/trivy-action action
-      # to avoid a few bugs
-      # scan the filesystem, rather than building a Docker image prior - the
-      # downside is we won't catch dependencies that are only installed in the
-      # image, but the upside is we'll only catch vulnerabilities that are
-      # explicitly in the our dependencies
+      # to avoid a few bugs.
+      #
+      # We scan the file system rather than building the Docker image to only scan
+      # our direct dependencies. The Docker images are still scanned by
+      # Vulnerability Observability:
+      #   - OSS: https://ops.grafana-ops.net/a/grafana-vulnerabilityobs-app/projects/sources/1
+      #   - Enterprise: https://ops.grafana-ops.net/a/grafana-vulnerabilityobs-app/projects/sources/12
+      #   (If these links are outdated, just go to the list and find the images manually.)
       run: |
         trivy fs \
           --scanners vuln \