Update UPGRADE-4.x.md

Co-authored-by: Javier Spagnoletti <phansys@gmail.com>

Author: wbloszyk

UPGRADE-4.x.md

@@ -8,7 +8,7 @@ UPGRADE FROM 4.x to 4.x
 
 - "sonata-project/datagrid-bundle" is bumped from ^2.4 to ^3.0.
 
-If you are extending these method you MUST add argument and return type declarations:
+  If you are extending these method you MUST add argument and return type declarations:
   - `Sonata\UserBundle\Entity\UserManager::getPager()`
   - `Sonata\UserBundle\Entity\GroupManager::getPager()`