Automatic toolchain upgrade to nightly-2025-04-19 (model-checking#4033)

Update Rust toolchain from nightly-2025-04-18 to nightly-2025-04-19
without any other source changes.

Co-authored-by: celinval <[email protected]>

Author: github-actions[bot]

rust-toolchain.toml

@@ -2,5 +2,5 @@
 # SPDX-License-Identifier: Apache-2.0 OR MIT
 
 [toolchain]
-channel = "nightly-2025-04-18"
+channel = "nightly-2025-04-19"
 components = ["llvm-tools", "rustc-dev", "rust-src", "rustfmt"]