Update actions/checkout in GitHub Actions workflows to v3

.github/workflows/book.yml

@@ -9,7 +9,7 @@ jobs:
     name: Build and deploy book
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: stable

.github/workflows/release.yml

@@ -38,7 +38,7 @@ jobs:
             rust: stable
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: ${{ matrix.rust }}

.github/workflows/test.yml

@@ -28,7 +28,7 @@ jobs:
             rust: stable
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: nanasess/setup-chromedriver@master
       - uses: actions-rs/toolchain@v1
         with: