message: Remove unnecessary serde pieces
  Summary: We previously had these with JSON derivations to help the --check --json flag in the binary. But that turned out to be explicitly unhelpful, so delete them.
diff: use codemap::{LineCol, SpanLoc};
  use gazebo::variants::VariantName;
  -use serde::{Deserialize, Serialize};
  use std::fmt::{self, Display};
  pub(crate) trait LintWarning: Display + VariantName {
  fn is_serious(&self) -> bool;
  }
  -#[derive(Copy, Clone, Hash, Eq, PartialEq, Debug, Serialize, Deserialize)]
  +#[derive(Copy, Clone, Hash, Eq, PartialEq, Debug)]
  pub struct LineCol1 {
  /// The line number within the file (1-indexed).
  pub line: usize,
  @@ -33,7 +32,7 @@ pub struct LineCol1 {
  pub column: usize,
  }
  -#[derive(Debug, Deserialize, Clone, Copy, Serialize)]
  +#[derive(Debug, Clone, Copy)]
  pub struct LineColSpan {
  pub begin: LineCol1,
  pub end: LineCol1,
  