minor #19389 [Console] Application update PHPDoc of add and register methods (SpacePossum)
minor #19389 [Console] Application update PHPDoc of add and register methods (SpacePossum)

This PR was squashed before being merged into the 2.7 branch (closes #19389).

Discussion
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[Console] Application update PHPDoc of add and register methods

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

The [PHPDoc](https://github.com/symfony/symfony/blob/2.7/src/Symfony/Component/Console/Application.php#L354) states the method will always return a command, but it doesn't. Since [Application::register](https://github.com/symfony/symfony/blob/2.7/src/Symfony/Component/Console/Application.php#L328) returns the result of `add` directly is also doesn't always return the command (as its PHPDoc states).

Commits
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6f0474f [Console] Application update PHPDoc of add and register methods

symfony/Console