Fix #7106: std domain: enumerated nodes are marked as duplicated

CHANGES

@@ -89,6 +89,8 @@ Bugs fixed
   modifier keys are ignored, which means the feature can interfere with browser
   features
 * #7090: std domain: Can't assign numfig-numbers for custom container nodes
+* #7106: std domain: enumerated nodes are marked as duplicated when extensions
+  call ``note_explicit_target()``
 
 Testing
 --------

sphinx/transforms/__init__.py

@@ -173,7 +173,9 @@ class AutoNumbering(SphinxTransform):
         domain = self.env.get_domain('std')  # type: StandardDomain
 
         for node in self.document.traverse(nodes.Element):
-            if domain.is_enumerable_node(node) and domain.get_numfig_title(node) is not None:
+            if (domain.is_enumerable_node(node) and
+                    domain.get_numfig_title(node) is not None and
+                    node['ids'] == []):
                 self.document.note_implicit_target(node)