Remove mentions of high availability

Removing mentions of high availability per request from GitLab
executive team.

doc/administration/monitoring/prometheus/index.md

@@ -114,7 +114,7 @@ prometheus['scrape_configs'] = [
 NOTE: **Note:**
 Prometheus and most exporters don't support authentication. We don't recommend exposing them outside the local network.
 
-A few configuration changes are required to allow GitLab to be monitored by an external Prometheus server. External servers are recommended for highly available deployments of GitLab with multiple nodes.
+A few configuration changes are required to allow GitLab to be monitored by an external Prometheus server. External servers are recommended for [GitLab deployments with multiple nodes](../../reference_architectures/index.md).
 
 To use an external Prometheus server:
 

doc/user/clusters/applications.md

@@ -933,8 +933,8 @@ vault:
   installed: true
 ```
 
-By default you will get a basic Vault setup with no high availability nor any scalable
-storage backend. This is enough for simple testing and small scale deployments, though has limits
+By default you will get a basic Vault setup with no scalable
+storage backend. This is enough for simple testing and small-scale deployments, though has limits
 to how much it can scale, and as it is a single instance deployment, you will experience downtime
 when upgrading the Vault application.