chore: remove crossbeam-skiplist cargo dep from cargo machete

It's now used in production code. It was previously used only for
benchmarking.

Author: josecelano

Cargo.toml

@@ -78,7 +78,7 @@ url = "2"
 uuid = { version = "1", features = ["v4"] }
 
 [package.metadata.cargo-machete]
-ignored = ["serde_bytes", "crossbeam-skiplist", "dashmap"]
+ignored = ["serde_bytes", "dashmap"]
 
 [dev-dependencies]
 local-ip-address = "0"