Update Rust crate schemars to 0.8.21

Author: oxide-renovate[bot]

Cargo.toml

@@ -15,7 +15,7 @@ prettyplease = "0.2.22"
 # Ideally we'd let you use no-std proptest, but proptest requires either the std
 # or the no_std option to be set. It won't compile without one of those two set.
 proptest = { version = "1.5.0", features = ["std"], default-features = false }
-schemars = "0.8.17"
+schemars = "0.8.21"
 serde = "1"
 serde_json = "1.0.115"
 syn = "2.0.48"