ACR build fails if the `--platform` flag is included in the Dockerfile

OS: All
Build Version: 20231030.6

Repro Steps:

1. Create a .NET MVC project by command dotnet new mvc -> Open it in VS Code and add docker support files.
   mvc.zip
2. Right click a container app environment -> Click "Create Container App..." -> Enter a name -> Select "Build from project remotely using Azure Container Registry" -> Select an azure container registry ->
   Select "+ Create new Azure Container Registry" -> Enter a name -> Select a SKU -> Select "Dockerfile" -> Enter -> Select "Linux" -> Skip for now -> Enable -> Select a HTTP traffic -> Enter.
3. Check whether succeeds to create a container app or not.

Expect:
Succeed to create a container app with the .NET MVC project.

Actual:
Fail to create a container app with the .NET MVC project.

Reproduce the failure with the attached mvc.zip project, a Dockerfile containing the --platform flag, and the VS Code "Create Container App" flow using a new Azure Container Registry. Trace the extension's remote Dockerfile build entry point and compare the request with a Dockerfile without that flag. Done means the .NET MVC project creates the container app successfully while retaining the --platform flag.