fixing the doctest in src/doc

Author: fchapoton

src/doc/en/thematic_tutorials/coercion_and_categories.rst

@@ -123,18 +123,15 @@ This base class provides a lot more methods than a general parent::
      'algebraic_closure',
      'an_embedding',
      'base_extend',
-     'divides',
      'epsilon',
      'extension',
      'fraction_field',
      'gen',
      'gens',
-     'integral_closure',
      'is_field',
      'ngens',
      'one',
      'order',
-     'prime_subfield',
      'random_element',
      'zero',
      'zeta',