Remove the hardcoded string used to create hostname for Linux dedicated

[soninaren]

The code referenced her is not executed any more because WEBSITE_HOSTNAME is configured on linux dedicated. We should consider removing this code.

azure-functions-host/src/WebJobs.Script/HostNameProvider.cs

Line 45 in 6c23426

_hostName = $"{websiteName}.azurewebsites.net";

[mathewc]

I know the code comment says WEBSITE_HOSTNAME isn't populated for Linux Dedicated which must have been the case at some point. You're saying that your testing shows that it now is?

If we were to remove this, what do we do if WEBSITE_HOSTNAME is empty? Are you saying it's ALWAYS populated on all SKUs/Environments? If so, then we'd probably throw an exception. Otherwise, we'll need to keep a fallback path like this it seems.