Cumuls readme container section

### Broken Link

First link in [cumulus documentation](https://github.com/polkadot-developers/substrate-docs/issues/new/choose), namely [container section](https://github.com/paritytech/polkadot-sdk/blob/a310df263de0755d2a00ad02fd5692810cf2d2a3/cumulus/docs/contributor/container.md) redirects to 404

### Expected Location

_No response_

### Context and Origin

_No response_