docs: add warning about roleRules replacing default rules

Add clear warning in values.yaml that enabling roleRules completely
replaces the default Role rules, requiring users to include all
necessary permissions for proper controller operation.

This addresses potential safety concerns where users might not realize
they need to include essential permissions like secrets, configmaps,
and applications access.

Signed-off-by: puretension <rlrlfhtm5@gmail.com>

Author: puretension

charts/argo-cd/values.yaml

@@ -1142,6 +1142,8 @@ controller:
 
   ## Enable this and set the rules: to whatever custom rules you want for the Role resource.
   ## Defaults to off
+  ## WARNING: When enabled, this completely replaces the default Role rules.
+  ## Ensure you include all necessary permissions for proper controller operation.
   roleRules:
     # -- Enable custom rules for the application controller's Role resource
     enabled: false