Update actions/checkout in GitHub Actions workflows to v4

Author: striezel

.github/workflows/build.yml

@@ -38,7 +38,7 @@ jobs:
       CARGO_TERM_COLOR: always
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
@@ -113,14 +113,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Build
         uses: ./.github/actions/zts
   test-embed:
     name: Test with embed
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Test
         uses: ./.github/actions/embed

.github/workflows/docs.yml

@@ -20,7 +20,7 @@ jobs:
         mdbook: ["latest"]
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with: