pythongh-115059: Remove debugging code in test_io (pythonGH-115240)

(cherry picked from commit 597fad0)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Lib/test/test_io.py

@@ -2437,36 +2437,6 @@ def test_interleaved_readline_write(self):
                 f.flush()
                 self.assertEqual(raw.getvalue(), b'1b\n2def\n3\n')
 
-    def test_xxx(self):
-        with self.BytesIO(b'abcdefgh') as raw:
-            with self.tp(raw) as f:
-                f.write(b'123')
-                self.assertEqual(f.read(), b'defgh')
-                f.write(b'456')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'123defgh456')
-        with self.BytesIO(b'abcdefgh') as raw:
-            with self.tp(raw) as f:
-                f.write(b'123')
-                self.assertEqual(f.read(3), b'def')
-                f.write(b'456')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'123def456')
-        with self.BytesIO(b'abcdefgh') as raw:
-            with self.tp(raw) as f:
-                f.write(b'123')
-                self.assertEqual(f.read1(), b'defgh')
-                f.write(b'456')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'123defgh456')
-        with self.BytesIO(b'abcdefgh') as raw:
-            with self.tp(raw) as f:
-                f.write(b'123')
-                self.assertEqual(f.read1(3), b'def')
-                f.write(b'456')
-                f.flush()
-                self.assertEqual(raw.getvalue(), b'123def456')
-
     # You can't construct a BufferedRandom over a non-seekable stream.
     test_unseekable = None