a doc is master by default

Author: kwankyu

src/sage_docbuild/conf.py

@@ -296,8 +296,8 @@ def set_intersphinx_mappings(app, config):
     intersphinx.normalize_intersphinx_mapping(app, config)
 
 
-# By default document are not master.
-multidocs_is_master = False
+# By default document is master.
+multidocs_is_master = True
 
 # https://sphinx-copybutton.readthedocs.io/en/latest/use.html
 copybutton_prompt_text = r"sage: |[.][.][.][.]: |\$ "