[doc] Fix minor typo in example/parametrize.rst

A space is needed for ``ZeroDivisionError`` to render as teletype.

doc/en/example/parametrize.rst

@@ -686,5 +686,5 @@ For example:
             assert (6 / example_input) == e
 
 In the example above, the first three test cases should run without any
-exceptions, while the fourth should raise a``ZeroDivisionError`` exception,
+exceptions, while the fourth should raise a ``ZeroDivisionError`` exception,
 which is expected by pytest.