[Bug] [self-hosted] platform for preset in onboarding config is modified to "local"

[morremeyer]

How are you running Renovate?

Self-hosted Renovate

If you're self-hosting Renovate, tell us which platform (GitHub, GitLab, etc) and which version of Renovate.

GitHub, renovate-ce 10.0.0 (renovate 40.11.18)

Please tell us more about your question or problem

We have the onboarding config set via RENOVATE_ONBOARDING_CONFIG, to the following:

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "extends": [
    "github>anaconda/renovate-config"
  ]
}

However, when the onboarding PR is opened, the preset is included as local>anaconda/renovate-config instead of github>anaconda/renovate-config.

I see this as a bug because it breaks the configuration when the repository is migrated to another git hosting provider/platform.

Since we and our internal users make use of the local platform for testing configurations, it also requires fixing the config for every repository.

I created a public reproduction repository at https://github.com/anaconda/renovate-reproduction.

Checking the onboarding PR anaconda/renovate-reproduction#1, you can see the current behaviour.

Logs (if relevant)

No response