[8.x](backport #4517) [apm] Update Applications nav subsection from "…

…Services" to "Service inventory" (#4519)

* [apm] Update Applications nav subsection from "Services" to "Service inventory" (#4517)

* update references to services item in serverless side bar

* update references to services item in stateful side bar

* scale back serverless updates

(cherry picked from commit a24b240)

# Conflicts:
#	docs/en/serverless/apm/apm-find-transaction-latency-and-failure-correlations.asciidoc
#	docs/en/serverless/apm/apm-get-started.asciidoc
#	docs/en/serverless/apm/apm-ui-services.asciidoc

* Delete docs/en/serverless directory

---------

Co-authored-by: Colleen McGinnis <[email protected]>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

docs/en/observability/apm/view-and-analyze/ui-overview/services.asciidoc

@@ -36,7 +36,7 @@ and enable the **Service groups feature**.
 
 To create a service group:
 
-. Navigate to **Observability** → **Applications** → **Services**.
+. Navigate to **Observability** → **Applications** → **Service inventory**.
 . Switch to **Service groups**.
 . Click **Create group**.
 . Specify a name, color, and description.

docs/en/observability/monitor-k8s/monitor-k8s-application-performance.asciidoc

@@ -210,7 +210,7 @@ kubectl apply -f demo.yml
 [discrete]
 === View your traces in {kib}
 
-To view your application's trace data, open {kib} and go to *{observability} → Services*.
+To view your application's trace data, open {kib} and go to *{observability} → Service inventory*.
 
 The Applications UI allows you to monitor your software services and applications in real-time:
 visualize detailed performance information on your services, identify and analyze errors,