minor #28675 [CS] Enforces null type hint on last position in phpDocs (carusogabriel)

This PR was merged into the 2.8 branch.

Discussion
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[CS] Enforces null type hint on last position in phpDocs

| Q             | A
| ------------- | ---
| Branch?       | 2.8
| Bug fix?      | no
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | -   <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | - <!-- required for new features -->

As a majority in our codebase, the `null` typehint usually comes in the last position in phpDocs.

Commits
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efbba25577 [CS] Enforces null type hint on last position in phpDocs

Author: nicolas-grekas

BinaryFileResponse.php

@@ -40,7 +40,7 @@ class BinaryFileResponse extends Response
      * @param int                 $status             The response status code
      * @param array               $headers            An array of response headers
      * @param bool                $public             Files are public by default
-     * @param null|string         $contentDisposition The type of Content-Disposition to set automatically with the filename
+     * @param string|null         $contentDisposition The type of Content-Disposition to set automatically with the filename
      * @param bool                $autoEtag           Whether the ETag header should be automatically set
      * @param bool                $autoLastModified   Whether the Last-Modified header should be automatically set
      */
@@ -60,7 +60,7 @@ public function __construct($file, $status = 200, $headers = array(), $public =
      * @param int                 $status             The response status code
      * @param array               $headers            An array of response headers
      * @param bool                $public             Files are public by default
-     * @param null|string         $contentDisposition The type of Content-Disposition to set automatically with the filename
+     * @param string|null         $contentDisposition The type of Content-Disposition to set automatically with the filename
      * @param bool                $autoEtag           Whether the ETag header should be automatically set
      * @param bool                $autoLastModified   Whether the Last-Modified header should be automatically set
      *

HeaderBag.php

@@ -197,7 +197,7 @@ public function remove($key)
      * @param string    $key     The parameter key
      * @param \DateTime $default The default value
      *
-     * @return null|\DateTime The parsed DateTime or the default value if the header does not exist
+     * @return \DateTime|null The parsed DateTime or the default value if the header does not exist
      *
      * @throws \RuntimeException When the HTTP header is not parseable
      */

Session/Storage/Handler/PdoSessionHandler.php

@@ -71,7 +71,7 @@ class PdoSessionHandler implements \SessionHandlerInterface
     private $pdo;
 
     /**
-     * @var string|null|false DSN string or null for session.save_path or false when lazy connection disabled
+     * @var string|false|null DSN string or null for session.save_path or false when lazy connection disabled
      */
     private $dsn = false;