minor #21677 [Serializer] Removed duplicate operation in camelcase de…

…normalization (gadelat)

This PR was submitted for the master branch but it was merged into the 2.7 branch instead (closes #21677).

Discussion
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[Serializer] Removed duplicate operation in camelcase denormalization

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

Commits
-------

32fcd91 [Serializer] Removed duplicate operation in camelcase denormalization

src/Symfony/Component/Serializer/NameConverter/CamelCaseToSnakeCaseNameConverter.php

@@ -76,7 +76,7 @@ public function denormalize($propertyName)
         }
 
         if (null === $this->attributes || in_array($camelCasedName, $this->attributes)) {
-            return $this->lowerCamelCase ? lcfirst($camelCasedName) : $camelCasedName;
+            return $camelCasedName;
         }
 
         return $propertyName;