Update FactoryDelegate doc block

Author: rmk135

src/dependency_injector/providers.c

@@ -1102,8 +1102,8 @@ cdef class FactoryDelegate(Delegate):
  def __init__(self, factory):
  """Initializer.
 
- :param provides: Value that have to be provided.
- :type provides: object
+ :param factory: Value that have to be provided.
+ :type factory: object
  """
  if isinstance(factory, Factory) is False:
  raise Error('{0} can wrap only {1} providers'.format(