Upgrade ouroboros to 0.18 to fix soundness issues

Summary:
Versions of ouroboros prior to 0.18 have several **unsoundness** issues:

* Version 0.18.0 now correctly refuses to compile unsound usages of with_mut, but requires Rust 1.63 or later.
* Version 0.17.0 reintroduces type parameter support, but requires at least version 1.60 of the Rust toolchain.
* Version 0.16.0 fixes a potential soundness issue but removes template parameter support.

Since we are past 1.63 it should be safe to upgrade this.

Reviewed By: shayne-fletcher

Differential Revision: D57914533

fbshipit-source-id: 8c80e33e6c9e752e2e80434da222f0146320633e

compiler/crates/schema/Cargo.toml

@@ -20,7 +20,7 @@ fnv = "1.0"
 graphql-syntax = { path = "../graphql-syntax" }
 intern = { path = "../intern" }
 lazy_static = "1.4"
-ouroboros = "0.15.6"
+ouroboros = "0.18.4"
 rayon = "1.9.0"
 schema-flatbuffer = { path = "../schema-flatbuffer" }
 serde = { version = "1.0.185", features = ["derive", "rc"] }