minor #32854 Ensure signatures for setUp|tearDown|setUpAfterClass|tea…

…rDownAfterClass methods in tests are compatible with phpunit 8.2 (luispabon)

This PR was squashed before being merged into the 4.3 branch (closes #32854).

Discussion
----------

Ensure signatures for setUp|tearDown|setUpAfterClass|tearDownAfterClass methods in tests are compatible with phpunit 8.2

| Q             | A
| ------------- | ---
| Branch?       | 4.3
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no
| Fixed tickets | symfony/symfony#32844
| License       | MIT
| Doc PR        | n/a

Please bear with me as this is my first pr to symfony. Branched off 4.3 as requested here: symfony/symfony#32844

Tests currently do not pass due to:

```
PHP Fatal error:  Declaration of Symfony\Bridge\Monolog\Logger::reset() must be compatible with Monolog\Logger::reset(): void in /home/luis/Projects/symfony/src/Symfony/Bridge/Monolog/Logger.php on line 23
```

Commits
-------

97bcb5da50 Ensure signatures for setUp|tearDown|setUpAfterClass|tearDownAfterClass methods in tests are compatible with phpunit 8.2

Tests/Session/Storage/Handler/MigratingSessionHandlerTest.php

@@ -20,7 +20,7 @@ class MigratingSessionHandlerTest extends TestCase
     private $currentHandler;
     private $writeOnlyHandler;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         $this->currentHandler = $this->createMock(\SessionHandlerInterface::class);
         $this->writeOnlyHandler = $this->createMock(\SessionHandlerInterface::class);

Tests/Session/Storage/Handler/RedisClusterSessionHandlerTest.php

@@ -13,7 +13,7 @@
 
 class RedisClusterSessionHandlerTest extends AbstractRedisSessionHandlerTestCase
 {
-    public static function setupBeforeClass()
+    public static function setUpBeforeClass(): void
     {
         if (!class_exists('RedisCluster')) {
             self::markTestSkipped('The RedisCluster class is required.');