Removed redundant QuerySet.all() calls in docs and tests.

Most QuerySet methods are mapped onto the Manager and, in general,
it isn't necessary to call .all() on the manager.

tests/postgres_tests/test_array.py

@@ -278,9 +278,7 @@ class TestQuerying(PostgreSQLTestCase):
         IntegerArrayModel.objects.create(field=[2, 3])
         self.assertSequenceEqual(
             NullableIntegerArrayModel.objects.filter(
-                field__in=IntegerArrayModel.objects.all().values_list(
-                    "field", flat=True
-                )
+                field__in=IntegerArrayModel.objects.values_list("field", flat=True)
             ),
             self.objs[2:3],
         )