Remove system parachains Polkadot and Kusama runtimes (#1737)

Since the Polkadot and Kusama runtimes are no longer in the repo, the
relevant systems parachains runtimes also need to be removed. More
context [here](https://github.com/paritytech/polkadot-sdk/issues/603)
and [here](https://github.com/paritytech/polkadot-sdk/pull/1731).

Removes the following:
- `asset-hub-kusama` and `asset-hub-polkadot`
- `bridge-hub-kusama` and `bridge-hub-polkadot`
- `collectives-polkadot`
- `glutton-kusama`

Partially solves #603 and adds to #1731.