Bump MSRV to 1.75.0 (#8205)

* Bump MSRV to 1.75.0

Coupled with today's release of 1.77.0. Today's release actually has
some nice functions and such I think we'll want to use in Wasmtime but
we'll need to wait 3 months to be able to use them.

* Fix dead code warning in onnx

Cargo.toml

@@ -140,7 +140,7 @@ authors = ["The Wasmtime Project Developers"]
 edition = "2021"
 # Wasmtime's current policy is that this number can be no larger than the
 # current stable release of Rust minus 2.
-rust-version = "1.74.0"
+rust-version = "1.75.0"
 
 [workspace.lints.rust]
 # Turn on some lints which are otherwise allow-by-default in rustc.

crates/wasi-nn/src/backend/onnxruntime.rs

@@ -48,7 +48,7 @@ impl BackendFromDir for OnnxBackend {
     }
 }
 
-struct ONNXGraph(Arc<Mutex<Session>>, ExecutionTarget);
+struct ONNXGraph(Arc<Mutex<Session>>, #[allow(dead_code)] ExecutionTarget);
 
 unsafe impl Send for ONNXGraph {}
 unsafe impl Sync for ONNXGraph {}