Update virtual-networks.md

Removing "Option" & "manual" wording for ways to deploy secured agent service.
We used to have automatic way, but not anymore.
Also adding a note that this is only way to do that right now.

Author: AhmadAbdullah91

articles/ai-services/agents/how-to/virtual-networks.md

@@ -77,7 +77,10 @@ For customers without an existing virtual network, the Standard Setup with Priva
 * A Microsoft-managed key vault is used by default. 
 
 
-### Option 1: manually deploy the bicep template
+### Manually deploy the bicep template
+
+> [!NOTE]
+> Bicep template is the only way available to deploy a network secured environment for Agent Services.
 
 1. To deploy and customize the bicep templates, [download the template from GitHub](https://github.com/azure-ai-foundry/foundry-samples/tree/main/samples/microsoft/infrastructure-setup/15-private-network-standard-agent-setup). Download the following from the `private-network-standard-agent-setup` folder:
     1. `main.bicep`
@@ -180,4 +183,4 @@ Our goal is to accelerate the development and deployment of AI agents without co
 
 
 ## What's next?
-You’ve now successfully configured a Network Secure Account and project, use the [quickstart](../quickstart.md) to create your first agent. 
+You’ve now successfully configured a Network Secure Account and project, use the [quickstart](../quickstart.md) to create your first agent.