ci: fix docs generation

docs/source/conf.py

@@ -77,7 +77,7 @@ release = "0.0.0"
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = "en"
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.