Fix autodetected vulnerabilities

[electronix]

cargo audit shows currently 6 vulnerabilities in the substraTEE-worker. Those should be fixed.

[murerfel]

Running cargo audit shows that most vulnerabilities come from dependencies of sp::core, which are not directly under our control.
In addition, there are vulnerabilities in the ws crate - and there are no fixes yet.

[clangenb]

• sp_core security issue is known and being tackled in substrate: RUSTSEC-2021-0076 and libsecp256k1 version in sp-core paritytech/substrate#9356. This will be resolved with a substrate update in the future.
• ws all the more reason to move away from this unmaintained crate and use jsonrpsee instead, which is already used for the sidechain block-gossiping.