minor #19759 [Console] Fix Application::setDefaultCommand() missing return in docblock (ogizanagi)

This PR was merged into the 3.2-dev branch.

Discussion
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[Console] Fix Application::setDefaultCommand() missing return in docblock

| Q             | A
| ------------- | ---
| Branch?       | master
| License       | MIT

Despite the fact IDEs are clever enough to make this useless, I think it's clearly part of the contract of this public method anyway 😄

Commits
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0165835 [Console] Fix Application::setDefaultCommand() missing return in docblock

src/Symfony/Component/Console/Application.php

@@ -1002,6 +1002,8 @@ class Application
      *
      * @param string $commandName     The Command name
      * @param bool   $isSingleCommand Set to true if there is only one command in this application
+     *
+     * @return self
      */
     public function setDefaultCommand($commandName, $isSingleCommand = false)
     {