Update CI action versions

Author: trowski

.github/workflows/ci.yml

@@ -37,7 +37,7 @@ jobs:
           git config --global core.eol lf
 
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -49,7 +49,7 @@ jobs:
         run: echo "::set-output name=dir::$(composer config cache-dir)"
 
       - name: Cache dependencies
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ${{ steps.composer-cache.outputs.dir }}
           key: composer-${{ runner.os }}-${{ matrix.php-version }}-${{ hashFiles('**/composer.*') }}-${{ matrix.composer-flags }}