Update STEAM_CONFIG_VDF secret

[mfbrantner]

Automatic deployment to Steam is currently failing.

Most likely, the STEAM_CONFIG_VDF secret needs to be updated.
AFAIK, this needs to happen every ~6 months.

Here are the steps that need to be taken to get the new value for the secret.

Instead of installing steamcmd locally, I recommend going through the steps using Docker:
docker run -it --rm --entrypoint "/bin/bash" steamcmd/steamcmd:ubuntu-22

The person updating the secret needs:

• Permissions to change secrets for the repository
• Access to the Steam developer account and the email associated with it