[TASK] Test PHP 8.3 and 8.4

Also drop prophecy workarounds since PHP 8.2 compatibility
has been enabled upstream.

.github/workflows/tests.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: ['7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2']
+        php: ['7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
 
     steps:
       - uses: actions/checkout@v2
@@ -28,13 +28,7 @@ jobs:
           find src/ tests/ -name '*.php' -print0 | xargs -0 -n1 -P4 php -dxdebug.mode=off -l >/dev/null
 
       - name: Install dependencies
-        if: ${{ matrix.php <= '8.1' }}
         run: composer update
 
-      - name: Install dependencies PHP 8.2
-        # @todo: Needed until prophecy (req by phpunit) allows PHP 8.2, https://github.com/phpspec/prophecy/issues/556
-        if: ${{ matrix.php > '8.1' }}
-        run: composer update --ignore-platform-req=php+
-
       - name: Run test suite
         run: vendor/bin/phpunit