Refs #23919 -- Removed six.<various>_types usage

Thanks Tim Graham and Simon Charette for the reviews.

tests/backends/tests.py

@@ -23,7 +23,6 @@ from django.test import (
     SimpleTestCase, TestCase, TransactionTestCase, mock, override_settings,
     skipIfDBFeature, skipUnlessDBFeature,
 )
-from django.utils import six
 from django.utils.six.moves import range
 
 from .models import (
@@ -101,7 +100,7 @@ class OracleTests(unittest.TestCase):
         # than 4000 chars and read it properly
         with connection.cursor() as cursor:
             cursor.execute('CREATE TABLE ltext ("TEXT" NCLOB)')
-            long_str = ''.join(six.text_type(x) for x in range(4000))
+            long_str = ''.join(str(x) for x in range(4000))
             cursor.execute('INSERT INTO ltext VALUES (%s)', [long_str])
             cursor.execute('SELECT text FROM ltext')
             row = cursor.fetchone()
@@ -419,7 +418,7 @@ class LastExecutedQueryTest(TestCase):
         sql, params = data.query.sql_with_params()
         cursor = data.query.get_compiler('default').execute_sql(CURSOR)
         last_sql = cursor.db.ops.last_executed_query(cursor, sql, params)
-        self.assertIsInstance(last_sql, six.text_type)
+        self.assertIsInstance(last_sql, str)
 
     @unittest.skipUnless(connection.vendor == 'sqlite',
                          "This test is specific to SQLite.")