dissect: drop partition removal code

dissect: drop partition removal code

This reverts a major chunk of 75d7e04eb4662a814c26010d447eed8a862f5ec1

Now that the loopback device code already destroys the partitions we
don't have to do this here anymore.

I am sure the right place to delete the partitions is in the loopback
code, since we really only should do that for loopback devices, see
bug #24431, and not on "real" block devices.

I am also not convinced dropping partitions the dissection logic doesn't
care about is a good idea, after all. The dissection stuff should
probably not consider itself the "owner" of the block devices it
analyzes, but take a more passive role: figure out what is what, but not
modify it.

Fixes: #24431