Fix: Update gatekeeper docs to include replicas example

General MR

Summary

Add an example of explicitly defining replicas for OPA gatekeeper for High availability. It is already set for replicas: 3 in the package by default, so I modified terminology to articulate that.

Looking at chart source (upstream) and docs, there is little mention of high-availability and any limitations to number of replicas.

Issues

Closes #1281 (closed)

docs/understanding-bigbang/package-architecture/opa-gatekeeper.md

@@ -51,7 +51,13 @@ gatekeeper:
 
 ## High Availability
 
-High availability is accomplished by increasing the replicas in the values file of this helm chart.
+High availability is accomplished by ensuring the replicas in the values file of this helm chart are > 1. By default, this chart is configured for high availability with `replicas: 3`.
+
+```yaml
+gatekeeper:
+  values:
+    replicas: 3
+```
 
 ## Single Sign on (SSO)