net: deflake TestAcceptTimeout again

This is a followup to CL 33257.

It looks like active close operation at passive open side sometimes
takes a bit long time on Darwin.

Fixes #17948.

Change-Id: Ida17639c4e66a43e1be1f74fd0ef3baddde25092
Reviewed-on: https://go-review.googlesource.com/33258
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/timeout_test.go

@@ -176,8 +176,6 @@ func TestAcceptTimeout(t *testing.T) {
 					t.Error(err)
 					return
 				}
-				var b [1]byte
-				c.Read(b[:])
 				c.Close()
 			}()
 		}