document deprecation of the scale option

Author: xabbuh

reference/forms/types/integer.rst

@@ -88,6 +88,11 @@ scale
 
 **type**: ``integer`` **default**: ``0``
 
+.. versionadded:: 4.2
+
+    The ``scale`` option is deprecated since Symfony 4.2 and will be removed
+    in 5.0.
+
 This specifies how many decimals will be allowed until the field rounds the
 submitted value (via ``rounding_mode``). This option inherits from
 :doc:`number </reference/forms/types/number>` type and is overriden to ``0`` for