chore(deps): update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/rust.yml

@@ -12,7 +12,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Build
         run: cargo build
       - name: Run tests
@@ -26,6 +26,6 @@ jobs:
   format:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Format Rust code
         run: cargo fmt --all -- --check