build(deps): bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/book.yml

@@ -24,7 +24,7 @@ jobs:
       contents: read
     steps:
       - name: Checkout the repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install Python dependencies
         run: |

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
     name: intro/hello-world
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: dtolnay/rust-toolchain@v1
         with:
@@ -40,7 +40,7 @@ jobs:
         project:
           ["intro/blinky", "intro/button", "intro/button-interrupt", "intro/hello-world", "intro/panic", "intro/http-client", "advanced/stack_overflow_detection"]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: dtolnay/rust-toolchain@v1
         with: