Remove repos from manifests which we aren't using anymore
Description
Remove repos from manifests which aren't being used anymore and move Gallery2 to a unified branch
Issues
https://gitlab.e.foundation/e/os/backlog/-/issues/3790
https://gitlab.e.foundation/e/os/backlog/-/issues/3791
https://gitlab.e.foundation/e/os/backlog/-/issues/3792
https://gitlab.e.foundation/e/os/backlog/-/issues/3794
https://gitlab.e.foundation/e/os/backlog/-/issues/3795