Update to v2 of the action

This should prevent upgrading to Composer v2 by mistake

Author: greg0ire

.github/workflows/continuous-integration.yml

@@ -59,7 +59,7 @@ jobs:
         uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP"
-        uses: "shivammathur/setup-php@1.8.2"
+        uses: "shivammathur/setup-php@v2"
         with:
           coverage: "none"
           php-version: "${{ matrix.php-version }}"
@@ -99,7 +99,7 @@ jobs:
         uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP"
-        uses: "shivammathur/setup-php@1.8.2"
+        uses: "shivammathur/setup-php@v2"
         with:
           coverage: "none"
           php-version: "${{ matrix.php-version }}"
@@ -133,7 +133,7 @@ jobs:
         uses: "actions/checkout@v2.0.0"
 
       - name: "Install PHP"
-        uses: "shivammathur/setup-php@1.8.2"
+        uses: "shivammathur/setup-php@v2"
         with:
           coverage: "none"
           php-version: "${{ matrix.php-version }}"