Revert "Add some regression test cases for denormalized float8 input."

Revert "Add some regression test cases for denormalized float8 input."

This reverts commit 500cf66d5522b39ddfdc26b309f8b5b0e385f42e.  As was
more or less expected, a small minority of platforms won't accept
denormalized input even with the recent changes.  It doesn't seem
especially helpful to test this if we're going to have to provide an
alternate expected-file to allow failure.