Refs #30547 -- Clarified that partial UniqueConstraints don't affect model validation.

docs/ref/models/constraints.txt

@@ -35,11 +35,12 @@ option.
 
     In general constraints are **not** checked during ``full_clean()``, and do
     not raise ``ValidationError``\s. Rather you'll get a database integrity
-    error on ``save()``. ``UniqueConstraint``\s are different in this regard,
-    in that they leverage the existing ``validate_unique()`` logic, and thus
-    enable two-stage validation. In addition to ``IntegrityError`` on
-    ``save()``, ``ValidationError`` is also raised during model validation when
-    the ``UniqueConstraint`` is violated.
+    error on ``save()``. ``UniqueConstraint``\s without a
+    :attr:`~UniqueConstraint.condition` (i.e. non-partial unique constraints)
+    are different in this regard, in that they leverage the existing
+    ``validate_unique()`` logic, and thus enable two-stage validation. In
+    addition to ``IntegrityError`` on ``save()``, ``ValidationError`` is also
+    raised during model validation when the ``UniqueConstraint`` is violated.
 
 ``CheckConstraint``
 ===================