bpo-40823: Use loadTestsFromTestCase() iso. makeSuite() in sqlite3 tests (GH-20538)

diff --git a/Lib/sqlite3/test/backup.py b/Lib/sqlite3/test/backup.py
index 3637c4b..ddff78c 100644
--- a/Lib/sqlite3/test/backup.py
+++ b/Lib/sqlite3/test/backup.py
@@ -162,7 +162,7 @@ def test_database_source_name(self):
 
 
 def suite():
-    return unittest.makeSuite(BackupTests)
+    return unittest.TestLoader().loadTestsFromTestCase(BackupTests)
 
 if __name__ == "__main__":
     unittest.main()