Fix installation of PHP dependencies in GitHub Actions

Ensure platform requirement (PHP) is checked to ensure the appropriate dependencies are installed.

For example, ignoring that the platform is PHP 8.0 would install a version of symfony/console that expectes PHP 8.1.

.github/workflows/continuous-integration.yml

@@ -64,21 +64,12 @@ jobs:
           max_attempts: 5
           command: composer require "vlucas/phpdotenv:${{ matrix.phpdotenv-version }}" --no-update --no-interaction
 
-      - name: Install PHP 7 dependencies
+      - name: Install PHP dependencies
         uses: nick-invision/retry@v1
         with:
           timeout_minutes: 5
           max_attempts: 5
           command: composer update --prefer-dist --no-interaction --no-progress
-        if: "matrix.php-version < 8"
-
-      - name: Install PHP 8 dependencies
-        uses: nick-invision/retry@v1
-        with:
-          timeout_minutes: 5
-          max_attempts: 5
-          command: composer update --prefer-dist --no-interaction --no-progress --ignore-platform-req=php
-        if: "matrix.php-version >= 8"
 
       - name: "Run PHP_CodeSniffer"
         run: "composer cs-check"