ci: update checkout version, switch rust caching

.github/workflows/ci.yml

@@ -19,17 +19,11 @@ jobs:
       RUST_BACKTRACE: 1
 
     steps:
-    - uses: actions/checkout@v2
-    - uses: dtolnay/[email protected]
-      with:
-        components: rustfmt
+    - uses: actions/checkout@v4
+    #- run: rustup toolchain install stable --profile minimal
+    - uses: Swatinem/rust-cache@v2
     - name: Check formatting
       run: cargo fmt -- --check
-    - name: Cargo cache
-      uses: actions/cache@v2
-      with:
-        key: ${{ runner.os }}-cargo-${{ hashFiles('Cargo.lock') }}
-        path: ~/.cargo/registry
     - name: Build
       run: cargo build --verbose -F crlf
     - name: Run tests