Update version of actions/checkout.

.github/workflows/rust.yml

@@ -14,20 +14,20 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Build
       run: cargo build --verbose
     - name: Run tests
       run: cargo test --verbose
   clippy_check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run Clippy
         run: cargo clippy --all-targets --all-features
   fmt_check:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Run cargo fmt check
         run: cargo fmt --all --check