minor symfony#61751 [PhpUnitBridge] use a compatible config file when running tests with PHPUnit 9.6 (xabbuh)

This PR was merged into the 7.4 branch.

Discussion
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[PhpUnitBridge] use a compatible config file when running tests with PHPUnit 9.6

| Q             | A
| ------------- | ---
| Branch?       | 7.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        |
| License       | MIT

Commits
-------

5e12ab2 use a compatible config file when running tests with PHPUnit 9.6

Author: xabbuh

.github/workflows/unit-tests.yml

@@ -265,4 +265,6 @@ jobs:
         env:
           SYMFONY_PHPUNIT_VERSION: '9.6'
         run: |
-          ./phpunit src/Symfony/Bridge/PhpUnit
+          cd src/Symfony/Bridge/PhpUnit
+          $COMPOSER_UP
+          $PHPUNIT -c phpunit-9.6.xml.dist

src/Symfony/Bridge/PhpUnit/.gitattributes

@@ -1,3 +1,4 @@
 /Tests export-ignore
 /phpunit.xml.dist export-ignore
+/phpunit-9.6.xml.dist export-ignore
 /.git* export-ignore

src/Symfony/Bridge/PhpUnit/phpunit-9.6.xml.dist

@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.6/phpunit.xsd"
+         backupGlobals="false"
+         colors="true"
+         bootstrap="vendor/autoload.php"
+         failOnRisky="true"
+         failOnWarning="true"
+>
+    <php>
+        <ini name="error_reporting" value="-1" />
+    </php>
+
+    <testsuites>
+        <testsuite name="Symfony PHPUnit Bridge Test Suite">
+            <directory>./Tests/</directory>
+            <directory suffix=".phpt">./Tests/DeprecationErrorHandler/</directory>
+        </testsuite>
+    </testsuites>
+
+    <coverage>
+        <include>
+            <directory>./</directory>
+        </include>
+        <exclude>
+            <directory>./Tests</directory>
+            <directory>./vendor</directory>
+        </exclude>
+    </coverage>
+</phpunit>