remove serde from deps

Signed-off-by: Benjamin Coenen <[email protected]>

Author: bnjjj

xtask/src/codegen/gen_lint_completions.rs

@@ -1,8 +1,6 @@
 //! Generates descriptors structure for unstable feature from Unstable Book
 use std::{
-    collections::HashMap,
     fs::File,
-    io::BufReader,
     io::Read,
     path::{Path, PathBuf},
 };