Update info about GitLab 13.5 and earlier

Update deprecation information. I created a subheading instead of
a deprecation note because our note structure can't support showing
a code example - and the code example can't be taken out of this
section. So, subheading it is.

doc/user/clusters/applications.md

@@ -665,14 +665,15 @@ applications you have configured. In case of pipeline failure, the
 output of the [Helm Tiller](https://v2.helm.sh/docs/install/#running-tiller-locally) binary
 is saved as a [CI job artifact](../../ci/pipelines/job_artifacts.md).
 
+#### Usage in GitLab versions 13.5 and below
+
 For GitLab versions 13.5 and below, the Ingress, Fluentd, Prometheus,
-and Sentry apps are fetched from the central Helm [stable
-repository](https://kubernetes-charts.storage.googleapis.com/), which
-is [scheduled for deletion](https://github.com/helm/charts#deprecation-timeline)
+and Sentry apps are fetched from the central Helm
+[stable repository](https://kubernetes-charts.storage.googleapis.com/), which
+[was deleted](https://github.com/helm/charts#deprecation-timeline)
 on November 13, 2020. This causes the installation CI/CD pipeline to
 fail. Upgrade to GitLab 13.6, or alternatively, you can
-use the following `.gitlab-ci.yml`, which has been tested on GitLab
-13.5:
+use the following `.gitlab-ci.yml`, which has been tested on GitLab 13.5:
 
 ```yaml
 include: