ACR url should deploy with Registry source as Azure Container Registry

When using the following action config, it will deploy to the webapp instance configured with the Registry source as "Private Registry" which makes the deployment fail requiring a username and password. With managed identity, it should be fine setting it to Azure Container Registry so the existing permissions allow a smooth experience.

Workaround: Change the Registry source to Azure Container Registry after the first deploy with the matching container, then future actions seem to apply that.

```
- name: Azure WebApp
uses: Azure/webapps-deploy@v2
with:
# Name of the Azure Web App
app-name: ${{ env.APP_NAME }}
# Applies to Web App Containers only: Specify the fully qualified container image(s) name. For example, 'myregistry.azurecr.io/nginx:latest' or 'python:3.7.2-alpine/'. For multi-container scenario multiple container image names can be provided (multi-line separated)
images: ${{ secrets.ACR_LOGIN_SERVER }}/myapp:${{ github.sha }}
# Enter the start up command. For ex. dotnet run or dotnet run
startup-command: /home/app/start.sh
```