Remove html_pygments_dark_style option

doc/theming.rst

@@ -66,8 +66,7 @@ Python :mod:`ConfigParser` module) and has the following structure:
 * The **pygments_dark_style** setting gives the name of a Pygments style to use
   for highlighting when the CSS media query ``(prefers-color-scheme: dark)``
   evaluates to true. It is injected into the page using
-  :meth:`~Sphinx.add_css_file()`. This can be overriden by the user in the
-  :confval:`html_pygments_dark_style` config value.
+  :meth:`~Sphinx.add_css_file()`.
 
 * The **sidebars** setting gives the comma separated list of sidebar templates
   for constructing sidebars.  This can be overridden by the user in the

doc/usage/configuration.rst

@@ -939,13 +939,6 @@ that use Sphinx's HTMLWriter class.
       The image file will be copied to the ``_static`` directory of the output
       HTML, but only if the file does not already exist there.
 
-.. confval:: html_pygments_dark_style
-
-   The style name to use for an additional Pygments stylesheet similar to
-   :confval:`pygments_style` . If not set and the theme defines a default
-   ``'pygments_dark_style'`` it will be used, otherwise no additional style
-   will be generated. See :doc:`/usage/theming` for further information.
-
 .. confval:: html_css_files
 
    A list of CSS files.  The entry must be a *filename* string or a tuple