steel-core: remove unnecessary direct dependencies in steel-core

Author: m4rch3n1ng

Cargo.lock

@@ -24,9 +24,7 @@ futures-task = "0.3.28"
 
 serde_json = "1.0.108"
 serde = { version = "1.0.193", features = ["derive", "rc"] }
-serde_derive = "1.0.193"
 bincode = "1.3.3"
-pretty = "0.12.1"
 im-lists = "0.9.0"
 
 strsim = "0.11.0"