update actions/checkout to v4

Author: rhysd

.github/workflows/ci.yaml

@@ -13,7 +13,7 @@ jobs:
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
       - name: Run tests
         run: cargo test --color always --all
@@ -23,7 +23,7 @@ jobs:
     name: Rust beta channel
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@beta
       - name: Run tests
         run: cargo test --color always --all
@@ -33,7 +33,7 @@ jobs:
     name: clippy and rustfmt
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt, clippy
@@ -43,7 +43,7 @@ jobs:
     name: examples
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
       - run: cargo run --example execute
       - run: cargo run --example wat
@@ -78,7 +78,7 @@ jobs:
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           submodules: true
       - uses: dtolnay/rust-toolchain@stable