Break: make meta optional

Cargo.toml

@@ -12,13 +12,14 @@ categories = ["parsing"]
 
 [features]
 default = []
+meta = ["dep:serde_json"]
 
 [dependencies]
 prost = "0.11.3"
 serde = { version = "1.0.148", features = ["derive"] }
 serde_bytes = "0.11.7"
 serde-pickle = "1.1.1"
-serde_json = "1.0.96"
+serde_json = { version = "1.0.96", optional = true }
 thiserror = "1.0.37"
 zip = { version = "0.6.3", default-features = false, features = ["deflate"] }