chore: simplify dep so serde=1 in Cargo.toml (#3664)

With this change, dependabot should just have to update `Cargo.lock` for
`serde`, e.g.:

- https://github.com/openai/codex/pull/3617
- https://github.com/openai/codex/pull/3618

codex-rs/file-search/Cargo.toml

@@ -17,5 +17,5 @@ clap = { version = "4", features = ["derive"] }
 ignore = "0.4.23"
 nucleo-matcher = "0.3.1"
 serde = { version = "1", features = ["derive"] }
-serde_json = "1.0.145"
+serde_json = "1"
 tokio = { version = "1", features = ["full"] }