Update initialize-sui-client-cli.mdx (#20202)

## Description 

Sui CLI defaults to testnet when a client.yaml does not exist and the
prompt is shown.

## Test plan 

How did you test the new or updated feature?

---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] REST API:

docs/content/snippets/initialize-sui-client-cli.mdx

@@ -13,7 +13,7 @@ Config file ["<FILE-PATH>/.sui/sui_config/client.yaml"] doesn't exist, do you wa
 Enter `y` to proceed. You receive the following response:
 
 ```
-Sui Full node server URL (Defaults to Sui Devnet if not specified) :
+Sui Full node server URL (Defaults to Sui Testnet if not specified) :
 ```
 
 Leave this blank (press Enter). You receive the following response: