Document acme_account_name cannot be changed on a role (#1998)

* Document acme_account_name cannot be changed on a role

* Apply suggestions from code review

Co-authored-by: Sarah Chavis <62406755+schavis@users.noreply.github.com>

---------

Co-authored-by: Sarah Chavis <62406755+schavis@users.noreply.github.com>

Author: stevendpclark

content/vault/v2.x (rc)/content/api-docs/secret/pki-external-ca.mdx

@@ -370,7 +370,7 @@ Roles define policies for certificate issuance, including which domains you can
 
 ### Create/update role
 
-Create or update a role.
+Create or update a role. You cannot modify `acme_account_name` after role creation.
 
 | Method | Path                              |
 |:-------|:----------------------------------|
@@ -380,7 +380,7 @@ Create or update a role.
 
 - `name` `(string: <required>)` - The name of the role.
 
-- `acme_account_name` `(string: <required>)` - The name of the ACME account to use for certificate requests.
+- `acme_account_name` `(string: <required>)` - The name of the ACME account to use for certificate requests. You cannot change the account name after role creation.
 
 - `allowed_domains` `(array<string>: [])` - List of domains the role accepts for certificates. You can use templates with ACL Path Templating (e.g., `{{identity.entity.name}}.example.com`).