Replaces actions-rs/toolchain with dtolnay/rust-toolchain (#34)

Replaces actions-rs/toolchain with dtolnay/rust-toolchain to setup rust. As actions-rs/toolchain is unmaintained, it causes a node version warning.

Author: tottoto

action.yml

@@ -31,9 +31,7 @@ runs:
   using: "composite"
   steps:
     - name: Install Rust
-      uses: actions-rs/[email protected]
-      with:
-        toolchain: stable
+      uses: dtolnay/rust-toolchain@stable
 
     - name: Install Kani
       shell: bash