minor #35274 [PHPUnitBridge] file_get_contents() expects parameter 3 to be resource (plozmun)

This PR was squashed before being merged into the 3.4 branch.

Discussion
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[PHPUnitBridge] file_get_contents() expects parameter 3 to be resource

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

file_get_contents 3rd parameter (context) expects resource or NULL to ignore them

Commits
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a28a42187c [PHPUnitBridge] file_get_contents() expects parameter 3 to be resource

Author: nicolas-grekas

bin/simple-phpunit

@@ -68,7 +68,7 @@ foreach ($defaultEnvs as $envName => $envValue) {
 $COMPOSER = file_exists($COMPOSER = $oldPwd.'/composer.phar')
     || ($COMPOSER = rtrim('\\' === DIRECTORY_SEPARATOR ? preg_replace('/[\r\n].*/', '', `where.exe composer.phar`) : `which composer.phar 2> /dev/null`))
     || ($COMPOSER = rtrim('\\' === DIRECTORY_SEPARATOR ? preg_replace('/[\r\n].*/', '', `where.exe composer`) : `which composer 2> /dev/null`))
-    ? (file_get_contents($COMPOSER, null, 0, 18) === '#!/usr/bin/env php' ? $PHP : '').' '.escapeshellarg($COMPOSER) // detect shell wrappers by looking at the shebang
+    ? (file_get_contents($COMPOSER, false, null, 0, 18) === '#!/usr/bin/env php' ? $PHP : '').' '.escapeshellarg($COMPOSER) // detect shell wrappers by looking at the shebang
     : 'composer';
 
 if (false === $SYMFONY_PHPUNIT_REMOVE = getenv('SYMFONY_PHPUNIT_REMOVE')) {