Remove unused dependencies

clippy_utils/Cargo.toml

@@ -5,23 +5,14 @@ authors = ["The Rust Project Developers"]
 edition = "2018"
 
 [dependencies]
-cargo_metadata = "0.12"
 if_chain = "1.0.0"
 itertools = "0.9"
-pulldown-cmark = { version = "0.8", default-features = false }
-quine-mc_cluskey = "0.2.2"
 regex-syntax = "0.6"
 serde = { version = "1.0", features = ["derive"] }
 smallvec = { version = "1", features = ["union"] }
 toml = "0.5.3"
 unicode-normalization = "0.1"
-semver = "0.11"
 rustc-semver="1.1.0"
-# NOTE: cargo requires serde feat in its url dep
-# see <https://github.com/rust-lang/rust/pull/63587#issuecomment-522343864>
-url = { version =  "2.1.0", features = ["serde"] }
-quote = "1"
-syn = { version = "1", features = ["full"] }
 
 [features]
 internal-lints = []