minor #49896 Apply no_null_property_initialization PHP-CS-Fixer rule …

…(yguedidi)

This PR was merged into the 6.3 branch.

Discussion
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Apply no_null_property_initialization PHP-CS-Fixer rule

| Q             | A
| ------------- | ---
| Branch?       | 6.3
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

After a discussion with `@stof`, this rule should be part of the ``@Symfony`` PHP-CS-Fixer ruleset.
This PR apply the rule on the Symfony code base.
see PHP-CS-Fixer/PHP-CS-Fixer#6876 for the PR on PHP-CS-Fixer

Commits
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2320c2a906 Apply no_null_property_initialization PHP-CS-Fixer rule

Tests/Console/Descriptor/TextDescriptorTest.php

@@ -17,7 +17,7 @@
 
 class TextDescriptorTest extends AbstractDescriptorTestCase
 {
-    private static $fileLinkFormatter = null;
+    private static $fileLinkFormatter;
 
     protected static function getDescriptor()
     {