CI: Add PHP 8.4 to the matrix

Author: alecpl

.github/workflows/tests.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        php: ['5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3']
+        php: ['5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
 
     name: PHP ${{ matrix.php }}/Linux
 
@@ -31,7 +31,7 @@ jobs:
       - name: Setup problem matchers
         run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
 
-      - name: Fix PHPUnit for PHP8
+      - name: Fix for PHP < 7.1
         run: composer remove phpstan/phpstan --dev --no-update
         if: matrix.php < 7.1