Ignore sphinx warning about unpickable cache (#7400)

[Sphinx 7.3.0][1] introduce a new warning about not being able to pickle
a config value. I think the function `plotly_sg_scraper` in
`sphinx_gallery_conf` is triggering this. If I read azure-pipelines.yml
correctly we are not preserving Sphinx's cache between runs anyway. So
we should be fine to just ignore this warning.

These new [config options][2] also require Sphinx 7.3.0.

[1]: https://www.github.com/sphinx-doc/sphinx/issues/12300
[2]: https://www.sphinx-doc.org/en/master/usage/configuration.html#confval-show_warning_types

doc/source/conf.py

@@ -63,6 +63,13 @@
 templates_path = ["_templates"]
 source_suffix = ".rst"
 
+show_warning_types = True
+suppress_warnings = [
+    # Ignore new warning in Sphinx 7.3.0 while pickling environment:
+    #   WARNING: cannot cache unpickable configuration value: 'sphinx_gallery_conf'
+    "config.cache",
+]
+
 # -- Options for HTML output -------------------------------------------------
 # https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-html-output
 

pyproject.toml

@@ -64,7 +64,7 @@ developer = [
     "tomli; python_version < '3.11'",
 ]
 docs = [
-    'sphinx>=7.2',
+    'sphinx>=7.3',
     'sphinx-gallery>=0.14',
     'numpydoc>=1.7',
     'sphinx-copybutton',

requirements/docs.txt

@@ -1,6 +1,6 @@
 # Generated via tools/generate_requirements.py and pre-commit hook.
 # Do not edit this file; modify pyproject.toml instead.
-sphinx>=7.2
+sphinx>=7.3
 sphinx-gallery>=0.14
 numpydoc>=1.7
 sphinx-copybutton