update rust toolchain

Summary:
It includes this fix which was backported to 1.62.1.
rust-lang/rust#98950

`2022-08-06` is what will become 1.64.0.

Changes are caused by:
- Split TypeVisitable from TypeFoldable: rust-lang/rust#98206
- Remove `fn backtrace` and replace with usages of provider API: rust-lang/rust#99431

Reviewed By: stepancheg

Differential Revision: D39277984

fbshipit-source-id: 5afc6c2b9e5ee3074ea0ede995868aef12cebf14

Author: KapJI

gazebo_lint/Cargo.toml

@@ -11,4 +11,5 @@ repository = "https://github.com/facebookincubator/gazebo_lint"
 plugin = true
 
 [dependencies]
+rustversion = "1.0"
 smallvec = "1.4"

gazebo_lint/src/lib.rs

@@ -72,7 +72,10 @@ use rustc_lint::LateLintPass;
 use rustc_lint::Lint;
 use rustc_lint::LintContext;
 use rustc_lint::LintId;
+#[rustversion::before(1.64)]
 use rustc_middle::ty::fold::TypeFoldable;
+#[rustversion::since(1.64)]
+use rustc_middle::ty::visit::TypeVisitable;
 use rustc_middle::ty::TyKind;
 use rustc_span::Span;
 use rustc_span::Symbol;