Automatic toolchain upgrade to nightly-2025-09-06 (#4339)

Update Rust toolchain from nightly-2025-09-05 to nightly-2025-09-06
without any other source changes.

---------

Co-authored-by: celinval <35149715+celinval@users.noreply.github.com>
Co-authored-by: Michael Tautschnig <tautschn@amazon.com>
Co-authored-by: Felipe R. Monteiro <felisous@amazon.com>

Author: 4 people

kani-driver/src/metadata.rs

@@ -177,7 +177,7 @@ pub mod tests {
 
     #[test]
     fn check_find_proof_harness_without_exact() {
-        let harnesses = vec![
+        let harnesses = [
             mock_proof_harness("check_one", None, None, None),
             mock_proof_harness("module::check_two", None, None, None),
             mock_proof_harness("module::not_check_three", None, None, None),
@@ -222,7 +222,7 @@ pub mod tests {
     fn check_find_proof_harness_with_exact() {
         // Check with exact match
 
-        let harnesses = vec![
+        let harnesses = [
             mock_proof_harness("check_one", None, None, None),
             mock_proof_harness("module::check_two", None, None, None),
             mock_proof_harness("module::not_check_three", None, None, None),

rust-toolchain.toml

@@ -2,5 +2,5 @@
 # SPDX-License-Identifier: Apache-2.0 OR MIT
 
 [toolchain]
-channel = "nightly-2025-09-05"
+channel = "nightly-2025-09-06"
 components = ["llvm-tools", "rustc-dev", "rust-src", "rustfmt"]