Removed unnecessary DBCacheTests.test_clear_commits_transaction test.

Was added in 44164c5c308da32a804dfb03ce0bffde2a6b4c56 but the
transaction.commit_unless_managed() line was removed in
ba5138b1c0253fcf390b7509ad7b954117b3be88; thus the test does nothing
but check that clear() runs.

tests/cache/tests.py

@@ -20,7 +20,7 @@ from django.core.cache import (
     DEFAULT_CACHE_ALIAS, CacheKeyWarning, cache, caches,
 )
 from django.core.cache.utils import make_template_fragment_key
-from django.db import connection, connections, transaction
+from django.db import connection, connections
 from django.http import HttpRequest, HttpResponse, StreamingHttpResponse
 from django.middleware.cache import (
     CacheMiddleware, FetchFromCacheMiddleware, UpdateCacheMiddleware,
@@ -971,13 +971,6 @@ class DBCacheTests(BaseCacheTests, TransactionTestCase):
         self.assertEqual(out.getvalue(),
             "Cache table 'test cache table' created.\n")
 
-    def test_clear_commits_transaction(self):
-        # Ensure the database transaction is committed (#19896)
-        cache.set("key1", "spam")
-        cache.clear()
-        transaction.rollback()
-        self.assertIsNone(cache.get("key1"))
-
 
 @override_settings(USE_TZ=True)
 class DBCacheWithTimeZoneTests(DBCacheTests):