docs: fix heading

Author: sinedied

docs/readme.md

@@ -92,7 +92,7 @@ The resource group and all the resources will be deleted.
 
 If you have any issue when running or deploying this sample, please check the [troubleshooting guide](./troubleshooting.md). If you can't find a solution to your problem, please [open an issue](https://github.com/Azure-Samples/openai-secure-ui-js/issues) in this repository.
 
-### Security
+## Security
 
 This sample has [Managed Identity](https://learn.microsoft.com/entra/identity/managed-identities-azure-resources/overview) built in to eliminate the need for developers to manage these credentials. Applications can use managed identities to obtain Microsoft Entra tokens without having to handle any secrets in the code. Additionally, we're using [Microsoft Security DevOps GitHub Action](https://github.com/microsoft/security-devops-action) to scan the infrastructure-as-code files and generates a report containing any detected issues.