Disable Rocks DB in the Parachain Node

[JoshOrndorff]

#136 allowed us to stop building rocks db which was wonderful both locally and in CI becuase it takes forever. #130 added parachain support, but brought with it a dependency from the parachain node to rocksdb again.

Here is part of the dependency tree from shortly before merging #130

$ cargo tree --invert rocksdb --depth 3
rocksdb v0.21.0
└── kvdb-rocksdb v0.19.0
    ├── polkadot-service v1.0.0 (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
    │   ├── cumulus-relay-chain-inprocess-interface v0.1.0 (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
    │   ├── cumulus-test-service v0.1.0 (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
    │   ├── polkadot-cli v1.1.0 (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
    │   └── polkadot-test-service v1.0.0 (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
    └── sc-client-db v0.10.0-dev (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
        ├── frame-benchmarking-cli v4.0.0-dev (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
        ├── polkadot-service v1.0.0 (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16) (*)
        ├── sc-cli v0.10.0-dev (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
        ├── sc-service v0.10.0-dev (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
        ├── sc-storage-monitor v0.1.0 (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)
        └── substrate-test-client v2.0.1 (https://github.com/off-narrative-labs/polkadot-sdk?branch=tuxedo-v1.3.0#5fbfba16)

[JoshOrndorff]