comment explaining empty list of disabled reftypes

Co-authored-by: Kevin Albertson <[email protected]>

Author: rcsanchez97

Diff for: src/libmongoc/doc/conf.py

@@ -29,6 +29,9 @@
 exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
 master_doc = 'index'
 
+# Set an empty list of disabled reftypes.
+# Sphinx 5.0 disables "std:doc" by default.
+# Many documentation references use :doc:
 intersphinx_disabled_reftypes = []
 
 # don't fetch libbson's inventory from mongoc.org during build - Debian and