remove cranelift-codegen from readme

Author: lqd

collector/benchmarks/README.md

@@ -19,8 +19,6 @@ They mostly consist of real-world crates.
   one in the Rust ecosystem.
 - **clap-3.1.6**: A command line argument parser. A crate used by many Rust
   programs.
-- **cranelift-codegen**: The largest crate from a code generator. Used by
-  Firefox.
 - **cranelift-codegen-0.82.1**: The largest crate from a code generator. Used by
   wasmtime.
 - **diesel**: A type safe SQL query builder. Utilizes the type system to