Set sphinx configuration file path explicitly to docs/conf.py

Xref https://about.readthedocs.com/blog/2024/12/deprecate-config-files-without-sphinx-or-mkdocs-config/

Author: weiji14

.readthedocs.yml

@@ -6,6 +6,10 @@ build:
   tools:
     python: "mambaforge-23.11"
 
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  configuration: docs/conf.py
+
 # Optionally set the version of Python and requirements required to build your docs
 conda:
   environment: ci/doc.yml