[VSCode] - Unable to change target framework version after initial selection

When using VS Code + Azure Functions extension, the first time you create a new Azure Function you are prompted whether you want to use the Beta templates or v1 templates. After making this selection, on every subsequent creation of an Azure Function you no longer are prompted for v1 or beta, and instead your previous selection has "stuck" and is (seemingly) unchangeable.

## Repro Steps
1. Perform a fresh installation of [VSCode (latest stable)](https://code.visualstudio.com/Download) and the [Azure Functions extension for VSCode](https://marketplace.visualstudio.com/items?itemName=ms-azuretools.vscode-azurefunctions)
1. Create a new Azure Function via the Extension's UI

You'll be prompted to install the templates:
Which then asks you which version:

Choose either, but take note which one you pick.
You'll see in your output window:
~~~
Downloading .NET templates for Azure Functions...
Installing "microsoft.azurefunctions.projecttemplates.1.0.3.10168"
Installing "azure.functions.templates.1.0.3.10168"
Finished installing Azure Functions templates.
...
The template "Azure Functions" was created successfully.
Finished running command: "dotnet new azureFunctionsProjectTemplates ".
Using "C#" as the project language...
Using "~1" as the project runtime...
~~~
3. Open a new VSCode workspace in an empty folder
3. Create a new Azure Function project via the Extension UI, observe you don't get to pick beta or v1

## Expected behavior
I'd expect to be prompted each time which type of Function I want to create. Sometimes I may be ok with a beta/preview Function runtime, other times I may be creating one for production and therefore want to be using v1/stable. This is consistent with how VS2017 prompts the user each time upon Function Project Creation.

## Workarounds
One must uninstall the templates before creating a new Azure Function Project that targets a different Functions SDK version.