[6.0.x] Fixed #36660 -- Fixed a regression in descending Index local field checks.

Regression in 8638d8bf74.

Refs #36273.

Thanks Federico Bond for the report.

Backport of edde2891c3 from main.

tests/invalid_models_tests/test_models.py

@@ -185,6 +185,15 @@ class IndexesTests(TestCase):
             ],
         )
 
+    def test_pointing_to_desc_field(self):
+        class Model(models.Model):
+            name = models.CharField(max_length=100)
+
+            class Meta:
+                indexes = [models.Index(fields=["-name"], name="index_name")]
+
+        self.assertEqual(Model.check(databases=self.databases), [])
+
     def test_pointing_to_m2m_field(self):
         class Model(models.Model):
             m2m = models.ManyToManyField("self")