meta: repo: remove references to ostc-eu.org
## Value
Long term reproducibility EF should host all code
## Description
Current manifest use reference to external domain:
```
default.xml: <remote name="ostc" fetch="https://git.ostc-eu.org/" />
```
## In scope
Related-tickets:
* https://git.ostc-eu.org/OSTC/packaging/git-repo/-/issues/5
* https://gitlab.eclipse.org/eclipse/oniro-core/oniro/-/issues/787
## Out of Scope
Blueprints should do same their side:
## Acceptance Criteria
no more reference to ostc-eu.org (or "booting" alias) should be present in sources
## Applicable Personas
* Product Integrator
issue