update actions/checkout in GitHub Actions workflows to v3

Author: striezel

.github/workflows/build.yml

@@ -26,7 +26,7 @@ jobs:
             phpts: ts
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
@@ -84,6 +84,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Build
         uses: ./.github/actions/zts

.github/workflows/docs.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
@@ -38,4 +38,4 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           BRANCH: gh-pages
           FOLDER: guide/book
-          CLEAN: true
+          CLEAN: true