Disable godot-fmt benchmark; its criterion pulls in too many dependencies although never used

Can be manually re-enabled. Unfortunately, Cargo doesn't offer optional dev-dependencies.

Also remove unused serde_json dependency.

Author: Bromeon

godot-core/Cargo.toml

@@ -31,7 +31,6 @@ serde = { version = "1", features = ["derive"], optional = true }
 # Reverse dev dependencies so doctests can use `godot::` prefix
 [dev-dependencies]
 godot = { path = "../godot" }
-serde_json = "1.0"
 
 [build-dependencies]
 godot-bindings = { path = "../godot-bindings" }

godot-fmt/Cargo.toml

@@ -8,9 +8,13 @@ edition = "2021"
 [dependencies]
 proc-macro2 = "1"
 
-[dev-dependencies]
-criterion = "0.3"
 
-[[bench]]
-name = "gdext_bench"
-harness = false
+# Disabled below, since it pulls in too many dependencies during `cargo test` but is not really used.
+# Dev-dependencies cannot be optional and feature-gated. Enable manually when needed.
+
+#[[bench]]
+#name = "gdext_bench"
+#harness = false
+#
+#[dev-dependencies]
+#criterion = "0.5"

godot-fmt/benches/gdext_bench.rs

@@ -4,6 +4,10 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
  */
 
+// IMPORTANT: to enable this benchmark, uncomment the corresponding lines in Cargo.toml.
+// Also disable clippy lints, as they run unconditionally.
+#![allow(clippy::all)]
+
 use std::{path::PathBuf, str::FromStr};
 
 use criterion::{black_box, criterion_group, criterion_main, Criterion};