Skip test for Python versions before 3.11

Author: fizzi01

tests/test_tcp.py

@@ -1264,7 +1264,8 @@ class _TestSSL(tb.SSLTestCase):
     TIMEOUT = 60
 
     def test_start_tls_buffer_transfer(self):
-        if self.implementation == 'asyncio':
+        if self.implementation == 'asyncio' and sys.version_info < (3, 11):
+            # StreamWriter.start_tls() introduced in Python 3.11
             raise unittest.SkipTest()
 
         HELLO_MSG = b'1' * self.PAYLOAD_SIZE