Merge branch '4.3' into 4.4

OskarStark · OskarStark · commit 08d444739544 · 2019-06-11T08:57:16.000+02:00
* 4.3:
  [Serializer] Use pack to install
diff --git a/serializer.rst b/serializer.rst
@@ -19,7 +19,7 @@ install the serializer before using it:
 
 .. code-block:: terminal
 
-    $ composer require symfony/serializer
+    $ composer require symfony/serializer-pack
 
 Using the Serializer Service
 ----------------------------
