Make the toc.circular suppress_warnings flag apply to self referenced…

… toctrees

Fixes #7410 (comment).

sphinx/environment/__init__.py

@@ -584,7 +584,9 @@ def collect_relations(self) -> Dict[str, List[str]]:
 
         def traverse_toctree(parent: str, docname: str) -> Iterator[Tuple[str, str]]:
             if parent == docname:
-                logger.warning(__('self referenced toctree found. Ignored.'), location=docname)
+                logger.warning(__('self referenced toctree found. Ignored.'),
+                               location=docname, type='toc',
+                               subtype='circular')
                 return
 
             # traverse toctree by pre-order