Fixed #32178 -- Allowed database backends to skip tests and mark expected failures.

Co-authored-by: Tim Graham <timograham@gmail.com>

tests/model_fields/test_charfield.py

@@ -1,7 +1,5 @@
-from unittest import skipIf
-
 from django.core.exceptions import ValidationError
-from django.db import connection, models
+from django.db import models
 from django.test import SimpleTestCase, TestCase
 
 from .models import Post
@@ -22,7 +20,6 @@ class TestCharField(TestCase):
     def test_lookup_integer_in_charfield(self):
         self.assertEqual(Post.objects.filter(title=9).count(), 0)
 
-    @skipIf(connection.vendor == 'mysql', 'Running on MySQL requires utf8mb4 encoding (#18392)')
     def test_emoji(self):
         p = Post.objects.create(title='Smile 😀', body='Whatever.')
         p.refresh_from_db()