[Bug]: Docker: Self signed cert env-vars not working anymore

### Verified issue does not already exist?

- [x] I have searched and found no existing issue

### What happened?

Self signed certificates provided as Docker environment variables `ACTUAL_HTTPS_KEY` and `ACTUAL_HTTPS_CERT` are throwing the following electron error since version 2.4.0:
`Rejection: Error: error:0480006C:PEM routines::no start line`

Once the certificates are provided as files (`/data/config.json`, `/data/selfhost.crt`, `selfhost.key`), the error is gone and actual server is starting properly.

### How can we reproduce the issue?

- Set environment variables `ACTUAL_HTTPS_KEY` and `ACTUAL_HTTPS_CERT` to configure HTTPS with self signed certificates.
- Start the docker image `actualbudget/actual-server:2.4.0`
- Server won't start an throw the error `Rejection: Error: error:0480006C:PEM routines::no start line`

### Where are you hosting Actual?

Docker

### What browsers are you seeing the problem on?

_No response_

### Operating System

Linux