Update configuration.rst

Minor language change: "must" => "need"

Author: ThomasLandauer

configuration.rst

@@ -415,11 +415,11 @@ define a ``staging`` environment where the client can test the project before
 going to production:
 
 #. Create a configuration directory with the same name as the environment (in
-   this case, ``config/packages/staging/``);
+   this case, ``config/packages/staging/``).
 #. Add the needed configuration files in ``config/packages/staging/`` to
-   define the behavior of the new environment. Symfony loads first the files in
-   ``config/packages/*.yaml``, so you must only configure the differences with
-   those files;
+   define the behavior of the new environment. Symfony loads the 
+   ``config/packages/*.yaml`` files first, so you just need to configure the
+   differences to those files.
 #. Select the ``staging`` environment using the ``APP_ENV`` env var as explained
    in the previous section.