Devtunnel no longer forwarding Authorization header from source

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Describe the bug

The Aspire devtunnel resource behavior seems to have changed. I have a webhook where I configure an Authorization header value for the source to send along to an anonymous webhook for local development purposes (think of it as an API Key). This header is no longer making it from the devtunnel to my local environment when previously the Authorization: Bearer value was available.

Version Aspire.Hosting.DevTunnels v13.1.0

### Expected Behavior

The header to be passed along.

### Steps To Reproduce

_No response_

### Exceptions (if any)

_No response_

### .NET Version info

_No response_

### Anything else?

_No response_

Start with the Aspire.Hosting.DevTunnels v13.1.0 implementation and trace how source request headers are forwarded to the local webhook. Reproduce the webhook setup described in the issue and verify that the configured Authorization: Bearer header reaches the local environment.

Written by the indexing model from the issue text.