chore(deps): update actions/checkout action to v3 (#76)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     name: Coding Standard
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install PHP
         uses: shivammathur/setup-php@v2
@@ -36,7 +36,7 @@ jobs:
     name: PHPStan
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install PHP
         uses: shivammathur/setup-php@v2
@@ -63,7 +63,7 @@ jobs:
     name: PHP ${{ matrix.php }} Test ${{ matrix.dependencies }}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install PHP
         uses: shivammathur/setup-php@v2