minor #16876 [Serializer] Update serializer example using type hints (94noni)

This PR was submitted for the 6.0 branch but it was merged into the 4.4 branch instead.

Discussion
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[Serializer] Update serializer example using type hints

Hi, small proposition to upgrade code example here in the serializer doc using type hint on object to serialize to make example more robust from the input to output

Before continuing on this page, I want to ask if it is useful or not
Thank you!

Commits
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fd73939 Update serializer.rst

Author: javiereguiluz

components/serializer.rst

@@ -74,20 +74,20 @@ exists in your project::
 
     class Person
     {
-        private $age;
-        private $name;
-        private $sportsperson;
-        private $createdAt;
+        private int $age;
+        private string $name;
+        private bool $sportsperson;
+        private ?\DateTime $createdAt;
 
         // Getters
-        public function getName()
+        public function getAge(): int
         {
-            return $this->name;
+            return $this->age;
         }
 
-        public function getAge()
+        public function getName(): string
         {
-            return $this->age;
+            return $this->name;
         }
 
         public function getCreatedAt()
@@ -96,28 +96,28 @@ exists in your project::
         }
 
         // Issers
-        public function isSportsperson()
+        public function isSportsperson(): bool
         {
             return $this->sportsperson;
         }
 
         // Setters
-        public function setName($name)
+        public function setName(string $name): void
         {
             $this->name = $name;
         }
 
-        public function setAge($age)
+        public function setAge(int $age): void
         {
             $this->age = $age;
         }
 
-        public function setSportsperson($sportsperson)
+        public function setSportsperson(bool $sportsperson): void
         {
             $this->sportsperson = $sportsperson;
         }
 
-        public function setCreatedAt($createdAt)
+        public function setCreatedAt(\DateTime $createdAt = null): void
         {
             $this->createdAt = $createdAt;
         }