docs: remove memoization beta and add install note (argoproj#7380)

Signed-off-by: roofurmston <[email protected]>

docs/memoization.md

@@ -1,7 +1,5 @@
 # Step Level Memoization
 
-![beta](assets/beta.svg)
-
 > v2.10 and after
 
 ## Introduction
@@ -38,6 +36,9 @@ spec:
 ...
 ```
 
+!!! Note 
+    In order to use memoization it is necessary to add the verbs `create` and `update` to the `configmaps` resource for the appropriate (cluster) roles. In the case of a cluster install the `argo-cluster-role` cluster role should be updated, whilst for a namespace install the `argo-role` role should be updated.
+
 ## FAQs
 
 1. If you see errors like `"error creating cache entry: ConfigMap \"reuse-task\" is invalid: []: Too long: must have at most 1048576 characters"`,