Issue #19884: Avoid spurious output on OS X with Gnu Readline

Also adjust the test condition, because enable-meta-key was only added in
6.1, not 6.0.
diff --git a/Lib/test/test_readline.py b/Lib/test/test_readline.py
index 588043e..4c400ef 100644
--- a/Lib/test/test_readline.py
+++ b/Lib/test/test_readline.py
@@ -44,7 +44,7 @@
 
 class TestReadline(unittest.TestCase):
 
-    @unittest.skipIf(readline._READLINE_VERSION < 0x0600
+    @unittest.skipIf(readline._READLINE_VERSION < 0x0601
                      and "libedit" not in readline.__doc__,
                      "not supported in this library version")
     def test_init(self):