Docs: fix ogp_custom_meta_tags should be a list.

With tuples I get:

```pytb
Traceback (most recent call last):
  File "/home/mdk/src/python/python-docs-fr/.venv/lib/python3.13/site-packages/sphinx/events.py", line 404, in emit
    results.append(listener.handler(self.app, *args))
                   ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/mdk/src/python/python-docs-fr/.venv/lib/python3.13/site-packages/sphinxext/opengraph/__init__.py", line 266, in html_page_context
    context["metatags"] += get_tags(app, context, doctree, app.config)
                           ~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mdk/src/python/python-docs-fr/.venv/lib/python3.13/site-packages/sphinxext/opengraph/__init__.py", line 250, in get_tags
    [make_tag(p, c) for p, c in tags.items()]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + [make_tag(p, c, "name") for p, c in meta_tags.items()]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + config["ogp_custom_meta_tags"]
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
TypeError: can only concatenate list (not "tuple") to list
```

Author: JulienPalard

Doc/conf.py

@@ -576,11 +576,11 @@
     'image': '_static/og-image.png',
     'line_color': '#3776ab',
 }
-ogp_custom_meta_tags = ('<meta name="theme-color" content="#3776ab">',)
+ogp_custom_meta_tags = ['<meta name="theme-color" content="#3776ab">',]
 if 'create-social-cards' not in tags:  # noqa: F821
     # Define a static preview image when not creating social cards
     ogp_image = '_static/og-image.png'
-    ogp_custom_meta_tags += (
+    ogp_custom_meta_tags += [
         '<meta property="og:image:width" content="200">',
         '<meta property="og:image:height" content="200">',
-    )
+    ]