chore: pin GitHub Actions to commit SHAs

Author: nunomaduro

.github/workflows/tests.yml

@@ -16,10 +16,10 @@ jobs:
 
     steps:
     - name: Checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
     - name: Setup PHP
-      uses: shivammathur/setup-php@v2
+      uses: shivammathur/setup-php@accd6127cb78bee3e8082180cb391013d204ef9f # v2
       with:
         php-version: ${{ matrix.php }}
         tools: composer:v2