C, fix retvals info-field to be collapsible

Author: jakobandersen

sphinx/domains/c.py

@@ -3337,7 +3337,8 @@ def display_object_type(self) -> str:
                names=('param', 'parameter', 'arg', 'argument'),
                typerolename='expr', typenames=('type',)),
     GroupedField('retval', label=_('Return values'),
-                 names=('retvals', 'retval')),
+                 names=('retvals', 'retval'),
+                 can_collapse=True),
     Field('returnvalue', label=_('Returns'), has_arg=False,
           names=('returns', 'return')),
     Field('returntype', label=_('Return type'), has_arg=False,