Fix bug of Sphinx's .. code:: directive not recognizing :class: option

Sphinx's own .. code:: directive (but not docutils') does not recognise
the :class: option but only the :classes: option.  This is probably due
to an oversight that the user-visible option is called ``:class:`` while
the Python attribute is called ``classes`` (to not collide with the
keyword ``class``).

Fix it by checking for the option ``class`` instead of ``classes``.

CHANGES

@@ -38,6 +38,7 @@ Bugs fixed
 * #9670: html: Fix download file with special characters
 * #9649: HTML search: when objects have the same name but in different domains,
   return all of them as result instead of just one.
+* Fix bug ``.. code::`` not recognising ``:classes:`` option instead of ``:class:`` option.  The new behaviour is only to accept ``:class:``.
 
 Testing
 --------

sphinx/directives/patches.py

@@ -154,7 +154,7 @@ def run(self) -> List[Node]:
 
         code = '\n'.join(self.content)
         node = nodes.literal_block(code, code,
-                                   classes=self.options.get('classes', []),
+                                   classes=self.options.get('class', []),
                                    force='force' in self.options,
                                    highlight_args={})
         self.add_name(node)