minor #39792 [Config] Add \Symfony\Component\Config\Loader::load() return type (zerkms)

This PR was merged into the 4.4 branch.

Discussion
----------

[Config] Add \Symfony\Component\Config\Loader::load() return type

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | yes
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix https://github.com/symfony/symfony/issues/39761 <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        |
<!--
Replace this notice by a short README for your feature/bugfix. This will help people
understand your PR and can be used as a start for the documentation.

Additionally (see https://symfony.com/releases):
 - Always add tests and ensure they pass.
 - Never break backward compatibility (see https://symfony.com/bc).
 - Bug fixes must be submitted against the lowest maintained branch where they apply
   (lowest branches are regularly merged to upper ones so they get the fixes too.)
 - Features and deprecations must be submitted against branch 5.x.
-->

`Symfony\Component\Config\Loader::load()` is missing return type, added it for consistency and static analysis purposes.

Commits
-------

fec66e61c8 [Config] Add \Symfony\Component\Config\Loader::load() return type

src/Symfony/Component/Config/Loader/LoaderInterface.php

@@ -24,6 +24,8 @@ interface LoaderInterface
      * @param mixed       $resource The resource
      * @param string|null $type     The resource type or null if unknown
      *
+     * @return mixed
+     *
      * @throws \Exception If something went wrong
      */
     public function load($resource, $type = null);