Remove invalid test -- this test reads freed memory, from what I can tell
auto merge of #16797 : nikomatsakis/rust/remove-invalid-spsc_queue-test, r=alexcrichton

This test seems to read freed memory -- the peeked variable points into the queue, but then the pop operation removes the node from the queue and moves the enclosing `T` elsewhere, invalidating the `peeked` pointer.

r? @alexcrichton