bump dependency on bindgen for llvm22, 0.64 was removed from the toplevel Cargo.lock

should be harmless,
cf https://github.com/martinthomson/ohttp/commit/a2335b2e7ffb6805206bf8f59a5f60b9e6f98bb4
and https://github.com/martinthomson/ohttp/commit/bf6a983845cc0b540effb3a615e92d914dfcfd0b

Index: third_party/rust/ohttp/Cargo.toml
--- third_party/rust/ohttp/Cargo.toml.orig
+++ third_party/rust/ohttp/Cargo.toml
@@ -86,7 +86,7 @@ version = "0.9"
 default-features = false
 
 [build-dependencies.bindgen]
-version = "0.64"
+version = "0.69"
 features = ["runtime"]
 optional = true
 default-features = false
