Block Delete Function api in Linux Consumption

https://github.com/Azure/azure-functions-host/blob/dev/src/WebJobs.Script.WebHost/Controllers/FunctionsController.cs#L168

In Linux consumption, this api deletes the function on a single instance only. When a new instance gets assigned the deleted function will be revived back from WEBSITE_RUN_FROM_PACKAGE contents.
ZipDeploy is the only way to update deployments. To avoid confusion return 400 errors from this api back to clients.

Open src/WebJobs.Script.WebHost/Controllers/FunctionsController.cs at line 168 and trace the delete-function API entry point for Linux Consumption. Confirm the behavior described in the issue; done means this API returns HTTP 400 for that deployment mode, while ZipDeploy remains the update path.

Written by the indexing model from the issue text.