Merge pull request #1457 from Wiicolas/typo

Typo fix

docs/known_issues.md

@@ -28,7 +28,7 @@ class Product
     {
         $this->imageFile = $imageFile;
 
-        // Only change the updated af if the file is really uploaded to avoid database updates.
+        // Only change the updatedAt property if the file is really uploaded to avoid database updates.
         // This is needed when the file should be set when loading the entity.
         if ($this->imageFile instanceof UploadedFile) {
             $this->updatedAt = new \DateTime('now');