Update the checkout GitHub action to v4

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
           - beta
           - nightly
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install Rust ${{ matrix.rust }}
         uses: actions-rs/toolchain@v1
         with:
@@ -36,7 +36,7 @@ jobs:
     name: Cargo fmt
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
           components: rustfmt
@@ -46,5 +46,5 @@ jobs:
     name: Check dependencies
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: EmbarkStudios/cargo-deny-action@v1