Docs: Reword the section heading for clarity

doc/development/features_inside_dot_gitlab.md

@@ -16,7 +16,7 @@ When implementing new features, please refer to these existing features to avoid
 - [CODEOWNERS](../user/project/code_owners.md#set-up-code-owners): `.gitlab/CODEOWNERS`.
 - [Route Maps](../ci/review_apps/#route-maps): `.gitlab/route-map.yml`.
 - [Customize Auto DevOps Helm Values](../topics/autodevops/customize.md#customize-values-for-helm-chart): `.gitlab/auto-deploy-values.yaml`.
-- [GitLab managed apps CI/CD](../user/clusters/applications.md#usage): `.gitlab/managed-apps/config.yaml`.
+- [GitLab managed apps CI/CD](../user/clusters/applications.md#prerequisites): `.gitlab/managed-apps/config.yaml`.
 - [Insights](../user/project/insights/index.md#configure-your-insights): `.gitlab/insights.yml`.
 - [Service Desk Templates](../user/project/service_desk.md#using-customized-email-templates): `.gitlab/service_desk_templates/`.
 - [Web IDE](../user/project/web_ide/#web-ide-configuration-file): `.gitlab/.gitlab-webide.yml`.

doc/user/clusters/applications.md

@@ -54,7 +54,7 @@ Supported applications:
 - [PostHog](#install-posthog-using-gitlab-cicd)
 - [Prometheus](#install-prometheus-using-gitlab-cicd)
 
-### Usage
+### Prerequisites
 
 You can find and import all the files referenced below
 in the [example cluster applications
@@ -95,7 +95,7 @@ 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 earlier than 13.5
+#### Prerequisites in GitLab versions earlier than 13.5
 
 For GitLab versions 13.5 and earlier, the Ingress, Fluentd, Prometheus, and Sentry
 apps were fetched from the central Helm stable repository (`https://kubernetes-charts.storage.googleapis.com/`).