minor #39541 Remove void return type from test methods (OskarStark)

This PR was merged into the 4.4 branch.

Discussion
----------

Remove void return type from test methods

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | ---
| License       | MIT
| Doc PR        | ---

cc @nicolas-grekas

Commits
-------

f126cf1304 Remove void return type from test methods

src/Symfony/Bundle/SecurityBundle/Tests/DependencyInjection/Compiler/AddSecurityVotersPassTest.php

@@ -71,7 +71,7 @@ class AddSecurityVotersPassTest extends TestCase
         $this->assertCount(4, $refs);
     }
 
-    public function testThatVotersAreTraceableInDebugMode(): void
+    public function testThatVotersAreTraceableInDebugMode()
     {
         $container = new ContainerBuilder();
 
@@ -103,7 +103,7 @@ class AddSecurityVotersPassTest extends TestCase
         $this->assertCount(2, $voters, 'Incorrect count of voters');
     }
 
-    public function testThatVotersAreNotTraceableWithoutDebugMode(): void
+    public function testThatVotersAreNotTraceableWithoutDebugMode()
     {
         $container = new ContainerBuilder();
         $container->setParameter('kernel.debug', false);

src/Symfony/Bundle/TwigBundle/Tests/DependencyInjection/Compiler/ExceptionListenerPassTest.php

@@ -19,7 +19,7 @@ use Twig\Environment;
 
 class ExceptionListenerPassTest extends TestCase
 {
-    public function testExitsWhenTwigIsNotAvailable(): void
+    public function testExitsWhenTwigIsNotAvailable()
     {
         $builder = new ContainerBuilder();
         $builder->register('exception_listener', ExceptionListener::class);