minor #5383 DX: fail PHPUnit tests on warning (kubawerlos)

This PR was squashed before being merged into the 2.17 branch.

Discussion
----------

DX: fail PHPUnit tests on warning

Commits
-------

bf9b02c6a DX: fail PHPUnit tests on warning

phpunit.xml.dist

@@ -16,6 +16,7 @@
     convertNoticesToExceptions="true"
     convertWarningsToExceptions="true"
     enforceTimeLimit="true"
+    failOnWarning="true"
     processIsolation="false"
     stopOnFailure="false"
     timeoutForSmallTests="2"

tests/Fixer/FunctionNotation/RegularCallableCallFixerTest.php

@@ -123,7 +123,7 @@ final class RegularCallableCallFixerTest extends AbstractFixerTestCase
         ];
 
         if (\PHP_VERSION_ID < 80000) {
-            yield 'call by variable' => [
+            yield 'call by variable (PHP < 8.0)' => [
                 '<?php
                     $a{"b"}{"c"}(1, 2);
                 ',