minor #13827 [Serializer] Fix ClassMetadataFactory PHPDoc (dunglas)

This PR was merged into the 2.7 branch.

Discussion
----------

[Serializer] Fix ClassMetadataFactory PHPDoc

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
-------

0dba547 [Serializer] Fix ClassMetadataFactory PHPDoc

src/Symfony/Component/Serializer/Mapping/Factory/ClassMetadataFactory.php

@@ -59,9 +59,10 @@ class ClassMetadataFactory
      * configuration. At last, the new object is returned.
      *
      * @param string|object $value
+     *
      * @return ClassMetadata
+     *
      * @throws \InvalidArgumentException
-
      */
     public function getMetadataFor($value)
     {
@@ -111,6 +112,7 @@ class ClassMetadataFactory
      * Checks if class has metadata.
      *
      * @param mixed $value
+     *
      * @return bool
      */
     public function hasMetadataFor($value)
@@ -123,7 +125,8 @@ class ClassMetadataFactory
     /**
      * Gets a class name for a given class or instance.
      *
-     * @param $value
+     * @param mixed $value
+     *
      * @return string|bool
      */
     private function getClass($value)