added Isolate your test instance warning to Snapshot restore doc (#1277)

Please go to the `Preview` tab and select the appropriate template:

* [HCP services](?expand=1&template=hcp_pull_request_template.md)
* [Terraform
Enterprise](?expand=1&template=ptfe_release_pull_request_template.md)

added Isolate your test instance warning to Snapshot restore doc

Author: gerardma77

content/vault/v1.20.x/content/docs/sysadmin/snapshots/restore.mdx

@@ -18,6 +18,16 @@ Manually restore data for a Vault cluster leader node with a saved snapshot.
   original cluster unseal keys to unseal Vault after restoring the snapshot.
 - **You must have permission to access encrypted data in backed storage**.
 
+<Warning title="Isolate your test instance">
+
+Always perform your upgrade and restore tests in a fully isolated network
+environment to avoid accidentally revoking 3rd-party credentials (secrets, etc.)
+and to maintain data consistency by preventing unwanted cluster-to-cluster
+communication. If your test instance revokes live credentials, they may expire
+and result in irrevocable leases for the production cluster associated with the
+snapshot.
+
+</Warning>
 
 ## Step 1: Bring your Vault cluster back online
 

content/vault/v1.21.x/content/docs/sysadmin/snapshots/restore.mdx

@@ -18,6 +18,16 @@ Manually restore data for a Vault cluster leader node with a saved snapshot.
   original cluster unseal keys to unseal Vault after restoring the snapshot.
 - **You must have permission to access encrypted data in backed storage**.
 
+<Warning title="Isolate your test instance">
+
+Always perform your upgrade and restore tests in a fully isolated network
+environment to avoid accidentally revoking 3rd-party credentials (secrets, etc.)
+and to maintain data consistency by preventing unwanted cluster-to-cluster
+communication. If your test instance revokes live credentials, they may expire
+and result in irrevocable leases for the production cluster associated with the
+snapshot.
+
+</Warning>
 
 ## Step 1: Bring your Vault cluster back online