Remove unused object.opEquals(TypeInfo, TypeInfo)

It seems that just had been forgotten to remove it when [bug 3917](http://d.puremagic.com/issues/show_bug.cgi?id=3917) was fixed.

Discussion: http://forum.dlang.org/thread/CAFDvkcu2z5duAE+BWwXg5r0GuGmFdLa69LojLqrnHqZq3H5ohA@mail.gmail.com