chore: tracing be compat with rustc_log

The current version of rustfix cannot be used in rust-lang/rust due
to the dependency on `tracing`. `tracing-core` is currently locked
to 0.1.30, which is too old for the version in the cargo repo
(it looks like they are trying to avoid a known deadlock).

See: https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/rustfix.20is.20incompatible.20with.20rust-lang.2Frust

Cargo.toml

@@ -95,7 +95,7 @@ thiserror = "1.0.50"
 time = { version = "0.3", features = ["parsing", "formatting", "serde"] }
 toml = "0.8.8"
 toml_edit = { version = "0.21.0", features = ["serde"] }
-tracing = "0.1.40"
+tracing = "0.1.37" # be compatible with rustc_log: https://github.com/rust-lang/rust/blob/e51e98dde6a/compiler/rustc_log/Cargo.toml#L9
 tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
 unicase = "2.7.0"
 unicode-width = "0.1.11"