Rephrase comment.

Lib/email/test/test_email.py

@@ -554,10 +554,10 @@ class TestEncoders(unittest.TestCase):
 
     def test_default_cte(self):
         eq = self.assertEqual
-        # With no explicit _charset its us-ascii, and all are 7-bit
+        # 7bit data and the default us-ascii _charset
         msg = MIMEText('hello world')
         eq(msg['content-transfer-encoding'], '7bit')
-        # Similar, but with 8-bit data
+        # Similar, but with 8bit data
         msg = MIMEText('hello \xf8 world')
         eq(msg['content-transfer-encoding'], '8bit')
         # And now with a different charset