removed obsolete versionadded-directive

Author: OskarStark

reference/forms/types/number.rst

@@ -44,11 +44,6 @@ Field Options
 scale
 ~~~~~
 
-.. versionadded:: 2.7
-
-    The ``scale`` option was introduced in Symfony 2.7. Prior to Symfony 2.7,
-    it was known as ``precision``.
-
 **type**: ``integer`` **default**: Locale-specific (usually around ``3``)
 
 This specifies how many decimals will be allowed until the field rounds