Replace DefaultAzureCredential auth flow diagram (Azure#17660)

* Replace DefaultAzureCredential auth flow diagram

* Delete old diagram

Author: scottaddie

sdk/azidentity/README.md

@@ -52,11 +52,11 @@ an Azure AD access token. See [Credential Types](#credential-types "Credential T
 
 `DefaultAzureCredential` is appropriate for most apps that will be deployed to Azure. It combines common production credentials with development credentials. It attempts to authenticate via the following mechanisms in this order, stopping when one succeeds:
 
-![DefaultAzureCredential authentication flow](img/DAC_flow.PNG)
+![DefaultAzureCredential authentication flow](img/mermaidjs/DefaultAzureCredentialAuthFlow.svg)
 
- - Environment - `DefaultAzureCredential` will read account information specified via [environment variables](#environment-variables) and use it to authenticate.
- - Managed Identity - If the app is deployed to an Azure host with managed identity enabled, `DefaultAzureCredential` will authenticate with it.
- - Azure CLI - If a user or service principal has authenticated via the Azure CLI `az login` command, `DefaultAzureCredential` will authenticate that identity.
+1. **Environment** - `DefaultAzureCredential` will read account information specified via [environment variables](#environment-variables) and use it to authenticate.
+2. **Managed Identity** - If the app is deployed to an Azure host with managed identity enabled, `DefaultAzureCredential` will authenticate with it.
+3. **Azure CLI** - If a user or service principal has authenticated via the Azure CLI `az login` command, `DefaultAzureCredential` will authenticate that identity.
 
 > Note: `DefaultAzureCredential` is intended to simplify getting started with the SDK by handling common scenarios with reasonable default behaviors. Developers who want more control or whose scenario isn't served by the default settings should use other credential types.