Upgrade toolchain to 2025-04-18 (model-checking#4031)

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under the terms of the Apache 2.0 and MIT licenses.

Author: zhassan-aws

rust-toolchain.toml

@@ -2,5 +2,5 @@
 # SPDX-License-Identifier: Apache-2.0 OR MIT
 
 [toolchain]
-channel = "nightly-2025-04-14"
+channel = "nightly-2025-04-18"
 components = ["llvm-tools", "rustc-dev", "rust-src", "rustfmt"]

tools/scanner/src/lib.rs

@@ -23,7 +23,7 @@ extern crate stable_mir;
 use crate::analysis::OverallStats;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::OutputType;
-use rustc_smir::{run_with_tcx, rustc_internal};
+use rustc_smir::run_with_tcx;
 use stable_mir::CompilerError;
 use std::ops::ControlFlow;
 use std::path::{Path, PathBuf};